Generally the moderators have nothing to do with the actual mathematical content of the posts. Their work is when the posts are incorrectly made (e.g. questions in answers, or comments in answers), or when spam is posted. Sometimes when blatantly crankish person is posting (although cranks often spam using sock puppets, and give other reasons for deletion, suspension, and whatnot).

One situation where the moderators should never be involved is when a user is posting a wrong answer. In that case the users should downvote, comment, or even vote to delete in some cases.

However what should happen when a user has accepted an answer which is clearly not an answer to the question posted? For example (that's not a real example, hopefully) if the user has asked a question regarding how is the function $\sin x$ can be approximated by polynomials, and the accepted answer states that $\sin x=\cos(\pi+x)$.

This sort of thing occurs often when a question is closed as a duplicate, or some other reason, and the OP just wants to gain those two points and accepts an answer (either without reading, or without trying to understand).

Question: Should the moderators intervene in a situation where an accepted answer is blatantly wrong? Should they delete the answer?

The reasons why moderators should be involved is that accepted answers cannot be deleted by the OP, and I'm not sure they can be deleted by community members. Moderators can force such deletion.

Of course this should only be after some comments have been pointed out that the answer is completely wrong for the question, and no attempts to correct the answer were made.

To clarify:

I am not suggesting, not even remotely, that the moderators will be referees, judges or graders of mathematical content. I am not suggesting to give the moderators a free hand in deleting accepted answers which are mathematically wrong.

However currently, if I were to flag an accepted answer which is not even wrong -- it doesn't answer the question, there is a reasonable chance that the flag is going to be declined. And that's fine in most cases where the community can "self-correct" and delete the post.

In the case of an accepted answer, however, there is no possibility that users delete the answer (perhaps with the exception of an obvious misuse of spam/offensive flags, which would penalize the answerer by a 100 points of reputation, and would be generally an abuse of the flagging system). Therefore if the community thinks an accepted answer should be deleted, they must seek the help of a moderator.

My intention in this meta thread was to raise this issue, and seek input from both the community and the moderators.

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    $\begingroup$ I post this because there is such question that I ran into some while ago, commented on the accepted answer, but nothing happened. I want to know whether or not this accepted answer is going to stay there forever, or not. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:03
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    $\begingroup$ On the other hand, there are some correct answers which are not accepted, not even upvoted. $\endgroup$ – leo Jul 12 '13 at 23:03
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    $\begingroup$ Without much forethought given to the implementation and use of the feature I'm about to describe, it would be neat if the accepted answer could be flagged next to the checkmark with something like the "exclamation point within triangle" warning in such cases. Like I said, this suggestion is probably riddled with problems, but it's just an idea. $\endgroup$ – rschwieb Jul 22 '14 at 12:26
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    $\begingroup$ Are you sure that 20K users can't delete an accepted answer? My vote to delete this answer has been recorded. Let's try to get it deleted, for science. $\endgroup$ – user147263 Mar 22 '15 at 1:49
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    $\begingroup$ I totally understand your frustration. I've been debating with the person who posted the accepted answer to <a>math.stackexchange.com/questions/1459375/…> for a while now and just can't budge him. I think this is mostly an issue for questions which quickly disappear since they don't get upvoted and noone sees them after a while. $\endgroup$ – DRF Oct 8 '15 at 17:00

I can think of a few valid reasons for moderator intervention regarding accepted answer:

  1. One user accepts another user's junk answers as a way of gaming the reputation system
  2. The answer owner requests deletion, having realized that the answer is totally wrong and being unable to get it unaccepted by the question owner (discussed in http://meta.math.stackexchange.com/q/9827)
  3. The accepted answer is correctly flagged as spam or offensive speech.

In the hypothetical example

user has asked a question regarding how is the function $\sin x$ can be approximated by polynomials, and the accepted answer states that $\sin x=\cos(\pi+x)$.

I can't rule out the possibility that the question owner found this answer the most helpful out of those given. If they already knew how to approximate $\cos x$, this answer does solve the problem. (This is not as far-fetched as one might think. I recently saw a question along the lines of "what should I add to sine wave to get $0$", where the answer was to add $-\sin x$, and this turned out to be what the OP was looking for.)

The accepted status of an answer does not prevent it from being downvoted into graying out and being commented upon, with critical comments raising to prominence through comment votes. I think this is quite enough.

To give a worse (still hypothetical) example: if someone asks

How to prove that the standard Cantor set has measure zero?

and accepts the answer

Since the real line is countable, so is the Cantor set, and countable sets have measure zero.

I would not want this to be an item on moderator's plate. Let the users deal with it. The accepted status of such an answer gives useful information about the question owner.

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    $\begingroup$ First of all, for the sake of discussion it is perfectly clear that the 2nd and 3rd reasons you gave are indisputable for when a moderator should intervene. The first one is also good, but less obvious to spot. Finally, the problem is that accepted answers are de jure the correct answers to the problem, rather than just being helpful - even more when the OP doesn't bother to comment on the accepted answer to indicate the helpfulness of the mistakes in the answer. If people (not well established users) see accepted answers as correct, [cont.] $\endgroup$ – Asaf Karagila Jul 2 '13 at 6:42
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    $\begingroup$ then it is important that we try to maintain the correctness of the accepted answers (at least those where the OP didn't comment on why a mistake was helpful). I'm not saying that moderators should referee or grade or anything, but this is also something that the community needs to figure out how to handle with the help of the moderators. $\endgroup$ – Asaf Karagila Jul 2 '13 at 6:43
  • $\begingroup$ I’ve upvoted on the basis of (2), (3), and the conclusion; (1) is hard enough to prove that I’d prefer to omit it from consideration. $\endgroup$ – Brian M. Scott Jul 3 '13 at 5:05
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    $\begingroup$ Your answer seems to overlook the fact that beyond being of debatable relevance to the question, $\sin x = \cos(\pi + x)$ is simply not a true identity. I assume that Asaf intended this, and this feature makes it a more interesting test case, to my mind. The question is: is there any reasonable sense in which a simply incorrect answer could be "most useful to the OP"? $\endgroup$ – Pete L. Clark Jul 3 '13 at 7:52
  • $\begingroup$ @BrianM.Scott Vote fraud is easy enough to prove with the tools moderators have available. But the answer acceptance would be only part of the vote fraud, and doesn't need any special rules. Posts created for the sole purpose of vote fraud that don't have any lasting value will be removed anyway when socks are dealt with. $\endgroup$ – user9733 Jul 3 '13 at 8:13
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    $\begingroup$ @MadScientist: Some simple-minded kinds of vote fraud are easy enough to prove. I doubt very much that one could prove a modest amount of intelligently limited collusion, even if one somehow came to suspect it. $\endgroup$ – Brian M. Scott Jul 3 '13 at 8:20
  • $\begingroup$ @BrianM.Scott vote fraud that would not be caught by a suspicious moderator investigating it is very hard to achieve on any significant scale. The tools we mods have for this are pretty extensive. I've seen users trying to evade the tools they suspected we have, but we still caught them. $\endgroup$ – user9733 Jul 3 '13 at 8:29
  • $\begingroup$ Late to comment, but here comes anyway. Something like 1 has actually happened a few times. It is not at all difficult to catch. Regular users can suspect it, flag a few posts, and those who are allowed peek among a few curtains will then investigate. BUT. Moderators, not forgetting about SE staff, have also more efficient tools for dealing with such problems. $\endgroup$ – Jyrki Lahtonen Jun 9 '16 at 16:39
  • $\begingroup$ what if it were just a bad answer and it was accepted asap to gain rep? $\endgroup$ – user64742 May 18 '17 at 23:30

Here is a protocol that could help in dealing with the situation, while preserving the spirit of not intervening based on mathematical judgement.

If a week or so passes in which the accepter does not respond, users with deletion rights can state in comments that they would like to delete the answer. The third such person then flags for moderation and a moderator deletes the answer.

  • $\begingroup$ That sounds reasonable, I'll flag as "not an answer", and we'll see what happens. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:13
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    $\begingroup$ Don t flag as not an answer: explain why the answer is wrong (and preferably do so in a comment, very explicitly. $\endgroup$ – Mariano Suárez-Álvarez Jul 1 '13 at 22:15
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    $\begingroup$ @Mariano: If I flag it by a custom flag then no one else is going to see this flag, and no three users will flag this answer. It's either one or the other. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:18
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    $\begingroup$ Well, unless I see a very explicit explanation of why the answer is wrong I will not act: I am not going to referee the site. $\endgroup$ – Mariano Suárez-Álvarez Jul 1 '13 at 22:20
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    $\begingroup$ @AsafKaragila You can flag, and leave a detailed comment, indicating the mistake(s), and that you are flagging, and linking to this answer. $\endgroup$ – Andrés E. Caicedo Jul 1 '13 at 22:23
  • $\begingroup$ @Mariano: This is exactly why I brought this up to the meta. So see what the moderators feel on the issue, and to get some input from other community members. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:24
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    $\begingroup$ @Andres: The problem is that my philosophy is try and minimize the feeling that a user may get that someone is "out to get him" (yeah, that whole MK drama got to me somehow). This is why I rarely vote to delete answers which are not really bad. For this reason I would avoid posting a direct link to a user's answer requesting it would be deleted. That is something better delegated to the moderators, in my eyes. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:32
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    $\begingroup$ I really think that the best approach is to write a comment on the wrong answer, explaining why it is wrong (and ideally adding another, correct answer) Moderators are not graders of the site, nor referees. $\endgroup$ – Mariano Suárez-Álvarez Jul 1 '13 at 22:39
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    $\begingroup$ @Mariano: Since I'm building this over an existing case - which I take to be the average scenario for initiating this sort of "protocol", let me point out that the question is closed, a correct answer exists (two of them, and one more which is more of a comment, but that's not the point), and I posted a comment pointing out why the answer is completely irrelevant to the question already in May. I don't mean to have the moderators as referees, graders, or any other way of judging the mathematical quality of the content here. This is just a case where a moderator intervention is inevitable. $\endgroup$ – Asaf Karagila Jul 1 '13 at 22:43
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    $\begingroup$ I’m very much opposed to this suggestion; I agree with Mariano’s heavily upvoted comment above (+8 as I write this). $\endgroup$ – Brian M. Scott Jul 3 '13 at 5:07
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    $\begingroup$ @Brian: Have you read my clarification? It really feels that you haven't. $\endgroup$ – Asaf Karagila Jul 3 '13 at 7:56
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    $\begingroup$ @Asaf: Yes, I’ve read it. I simply don’t think that an accepted answer should be deleted, no matter how wrong it is, unless it’s spam pure and simple. Acceptance is a matter for the OP. The rest of us can leave comments and/or downvote the answer. $\endgroup$ – Brian M. Scott Jul 3 '13 at 8:25
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    $\begingroup$ @Brian: You also feel that a lot more questions should be left open, and possibly undeleted (and perhaps some of those un-downvoted too). However the community is much larger than that. If three users capable of deleting a post decide to vote for deletion, then a post is deleted and that's the end of it. Except in the case of an accepted answer, where they can only try and explain why the post shouldn't be an answer to begin with. I understand that your philosophy is minimal intervention, but Mariano's comment, as well the other answers posted here, treat this post as if I suggest [...] $\endgroup$ – Asaf Karagila Jul 3 '13 at 8:30
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    $\begingroup$ @Brian: Isn't flagging a contest/exam question to be locked/deleted up to the judgment of the receiving moderator as well? Isn't everything we do is some sort of judgment? I'm expecting every single member on this site to apply some judgment, and even more so from the moderators whose work on the site is to apply judgment continuously about flags, about spam, about whatever. I do agree that the OP has the first right for deciding which answer should be accepted. But sometimes that judgment is clearly wrong, and even after pointing out that fact there is no change. [...] $\endgroup$ – Asaf Karagila Jul 3 '13 at 8:47
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    $\begingroup$ @Asaf: Caveat lector. That’s what comments are for (and downvotes, for those who use them). In such a case I’d not even mind if another answerer explicitly pointed out the problems in his own answer. $\endgroup$ – Brian M. Scott Jul 3 '13 at 8:50

I understand the sentiment; this happened to me. But what I see happened - and I hope this happens throughout - is that people came in and picked me up a bit. I downvoted the accepted solution (once it became clear that the poster of the accepted solution had no idea what he was doing), and the comments should make it clear to whoever reads the question/answers which one is correct.

It seems to me that the system as is works. The OP should decide which is correct, even if occasionally it leads to temporary wrongness. The crowd works to fix it in the long run. I do not think that the moderator has a role here.


I see that what I posted was not the issue - it is whether a clear non-answer is accepted. I am moved to think that the moderator should still not be involved unless the non-answer is offensive, etc.

  • $\begingroup$ (I flagged the incorrect answer for deletion.) $\endgroup$ – Andrés E. Caicedo Jul 3 '13 at 1:04
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    $\begingroup$ @AndresCaicedo: thank you very much. I'm glad the question is getting a little attention. BTW the problem was really nifty, but I simply do not understand why the OP accepted an answer whose author even admitted was incorrect. $\endgroup$ – Ron Gordon Jul 3 '13 at 1:15

There are surprisingly many seriously wrong but accepted answers with large numbers (sometimes over 100) of votes, some of them accepted instead of correct or clearly better answers. This type of false signal is hard to avoid in open registration internet sites that allow voting.

Whether answers are valid or not, Stackexchange answer acceptance is often lacking in rhyme or reason. Correcting a tiny bit of that noise is not worth the inconvenience to moderators and the bad precedent of making them judges of mathematical correctness.

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    $\begingroup$ The judgement is still with the community. I read Asaf's suggestion as moderators coming into play only after a +5 (say) comment that the answer is wrong, together with an ignored request for improvement, and a flag. That's effectively the community deciding and the mod only being the executioner. $\endgroup$ – Lord_Farin Jul 2 '13 at 18:11
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    $\begingroup$ The question did not say anything about votes on the comments playing a role. What you suggest is the addition of "blatantly wrong answer" as a new flag for deletion, or a new form of user votes to delete an answer instead of closing a question (and with no reputation barrier to doing so). These are a big enough deviation from the present philosophy that they ought to have a new proposal thread, if they are actually being proposed, and if anyone thinks that SE would implement such a big change to handle a small number of cases. $\endgroup$ – zyx Jul 2 '13 at 18:30
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    $\begingroup$ +1: Well said, and I agree basically with this answer. $\endgroup$ – Jonas Meyer Jul 3 '13 at 1:26
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    $\begingroup$ I find it very odd that this answer is so heavily downvoted, when it has so much in common with @ˈjuː.zɚ79365’s significantly upvoted answer and Mariano’s heavily upvoted comment under Michael’s answer. I don’t know whether the first sentence is accurate, but the rest is right on the money. $\endgroup$ – Brian M. Scott Jul 3 '13 at 5:13
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    $\begingroup$ @Brian: I actually downvoted both answers, but I can perfectly understand why the discrepancy. It's not only about the content it's also about how you deliver it. While I do agree with the content, I think it's a fairly obvious misinterpretation of my intentions (which is why I added the clarification). $\endgroup$ – Asaf Karagila Jul 3 '13 at 7:55

Here I report another singular case: this accepted answer is incorrect, in fact I downvoted, commented and flagged it, but

  • The flag was rejected, since it was based on technicalities, and I can comprehend that
  • The user who posted the answer isn't registered anymore on SE
  • here an user asked the same question (afterwards), so it should be flagged as duplicated, but this time there's a correct answer
  • the user was confounded since there were two opposite and both accepted answers

At this point I don't know what is the right thing to do. Flag the second question as duplicate? Try to contact a moderator to modify the delete the first question/answer? Leave everything as it is?

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    $\begingroup$ Certainly not bumping a question from five years ago on meta. You should have posted this as a separate question, and refer to this question in your new one. $\endgroup$ – Asaf Karagila Sep 28 '18 at 16:00

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