As an anonymous user, I gave an answer to this question:

Equivalence of two expressions for the Weeks manifold hyperbolic volume

I gave a link to a paper of Zagier which explains how one can write special values of Dedekind zeta functions (for fields with one complex place). The paper gives a clear explanation with references about how this arises by computing the volume of arithmetic hyperbolic manifolds in two ways: one using the volume formula for arithmetic manifolds, where the zeta function comes up, and the other using decompositions into ideal tetrahedra, where the dilogarithm comes up.

The OP responded in comments to my answer in a somewhat antagonistic manner, saying (in part, I don't remember exactly) that he needed a full answer to his question. It's the OP's prerogative to not vote up any answer if they like, of course, although the link in my answer really does explain what is going on (and even makes it clear how to do the explicit details if you really wanted to). But I generally find it best not to persist in these situations so I left a dismissive comment that began with "lol" and explained that I had no intention interacting any further with the OP. Even though I intended never to revisit the question again, I happened to see it in the question list as having "no answers" even though I had given one.

I can't tell what happened, and maybe I am mistaken, but it seems as though a high reputation user in a fit of pique deleted a perfectly good answer to a question. Maybe something else happened (the OP deleted the original question and asked it again, maybe? the effect is the same), but if my speculation is correct, that seems extremely contrary to the purported aims of this website.

Update: If the answer to a question is: "there is a standard technique in the field for showing why this is true, here is a paper which explains in detail the general principle" then what exactly is appropriate for an answer? A book length treatise on hyperbolic geometry?

To be clear, the answer was not just a link only answer, but it had a few sentences of discussion as well as precise reference to the particular paper which discusses the very essence of the question. I did indeed "summarize the content of the link." namely, the equality follows because you compute the volume in two different ways. Would it be better just to replace the link to the paper with the name of the paper and give the same answer? Someone could easily have edited it to this effect.

I genuinely think that it was a useful answer to the question to anyone who was willing and able to engage with the material. Moreover any full answer to this question requires a certain amount of sophistication and engagement with the material that I directly linked to. The fact that an undergraduate OP doesn't have that sophistication is not surprising, but answers are (supposedly) also supposed to be for other people who visit the site.

Update Update: Thanks for the explanation of the underlying process. The answer seems to have been (at least temporarily) resuscitated, so people can see for themselves if it is truly a "link-only" answer. The problem in this case seems to be that there is a gulf between the understanding of the OP and the answer. There's really no easy way to resolve this (Paramanand Singh in the comments suggests I could write five pages of explanation). But if it is the policy of the site to delete such answers, then I accept that.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Xander Henderson Mod
    May 31, 2021 at 15:28
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    $\begingroup$ The point of my 5 pages comment was not that you need to rewrite that particular answer to something like 5 pages, but that answers can be that long and still count as great answers. There are already many such answers on this site (some of them are just evaluating an integral and are quite long). On the other hand answers may be short. But the key thing is that they need to be self contained and not just a link answer. $\endgroup$
    – Paramanand Singh Mod
    Jun 5, 2021 at 3:54

2 Answers 2


At this point, the answer is deleted unilaterally. The timeline can be seen, it was voted to be deleted, then voted to be undeleted. Then a moderator decided to delete anyway (and converted to a comment).

I feel like this should remain as an answer, maybe with some slight improvements; it should include the full citation for the article (i.e. all bibliographic details) and maybe an additional sentence or two describing the method used. I think the nature of the question makes it impractical to give the "full explanation" as requested by the OP.

[Edit] I have taken the liberty to edit in the citation details, as well as some more exposition on the solution method taken from one of the poster's comments. Hopefully this is sufficient for this to be undeleted as an answer.

  • $\begingroup$ Did you miss the part where the answer was converted to a comment? It's still around. $\endgroup$
    – KReiser
    Jun 2, 2021 at 6:36
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    $\begingroup$ @KReiser I did not miss this fact, but the post does answer the question and I feel it should have been left as an answer (with some small improvements). $\endgroup$
    – xxxxxxxxx
    Jun 2, 2021 at 6:38
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    $\begingroup$ It might be better to also link to the springer page here, which is less likely to rot $\endgroup$ Jun 2, 2021 at 7:46
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    $\begingroup$ @ArcticChar and Morgan, I used the citation feature of math.SE to add a proper citation, which includes the DOI link (which is even less likely to rot). Perhaps if undeleted it should be turned into a community wiki answer $\endgroup$ Jun 2, 2021 at 7:54
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    $\begingroup$ @CalvinKhor Thank you! I tried to use the citation feature and it didn't seem to work for me, I guess I was unclear about exactly how to use it when it didn't autocomplete. Community Wiki seems a good option for this. $\endgroup$
    – xxxxxxxxx
    Jun 2, 2021 at 9:32
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    $\begingroup$ You’re welcome. The interface was a little confusing. I did it by searching for Zagier the logarithm function, clicking on the right paper, and then clicking on Add Citation in the bottom right. Or something like this, I cannot verify this ATM as the website does not let me open the dialogue box on mobile (!) $\endgroup$ Jun 2, 2021 at 10:03

There are two issues here:

  1. The rudeness of the asker. If someone is rude to you, raise a flag, and move on. Do not engage. Just raise a flag.

  2. The quality of your answer. The deleted answer is an example of a link-only answer—you gave a link to a paper, but gave almost no information about what that paper actually said. Answers on Math SE need to be self-contained. It is fine to link to offsite resources, but the answer you give here needs to be detailed enough that someone can get (at the very least) the basic outlines of an answer to the headline question without going offsite.

    Link-only answers (or citation-only answers) are deleted. Link-only answers do little to build the repository of questions and answers, and can suffer from link rot (I recently learned of a user to who posted a large number of links to their academic webpage; at some point, their institution moved things around, and all of the links broke, rending a large number of answers largely unintelligible).

    In this case, the answer was deleted by three members of the community, and the deletion had nothing to do with a "fit of pique".

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    $\begingroup$ Agree with 1. For 2, my answer was not link-only, even if it was "link-heavy". It's actually pretty clear to me from the CURED link that the OP pushed for it to be deleted for petty reasons. Clearly at the very least the information was useful and could have been converted to a comment. The actions in this case were a net negative for users of this site. $\endgroup$
    – Holmes
    May 31, 2021 at 0:44
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    $\begingroup$ @Holmes You are entitled to your opinion, and you are free to post the link as a comment, but the fact remains that your answer was insufficient. Three users voted to deleted, and I am in agreement with their decision. $\endgroup$
    – Xander Henderson Mod
    May 31, 2021 at 0:45
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    $\begingroup$ There is no doubt that the material as presented wasn't suitable for an answer : if something is heavy, then it's best to mention it as a comment and ask the OP how comfortable they are reading it. Where I do agree with Holmes is the fact that it should have been a comment, since the link seems useful. Perhaps, with a few clarifications in the comments, either OP or the answerer could have written a more detailed answer after coming to an understanding over the material. It's not the end of the matter : the question is still open and Moishe will hopefully try to write something up. $\endgroup$ May 31, 2021 at 4:21
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    $\begingroup$ This does open up a can of worms regarding links to extremely heavy topics , because it's difficult to be placing all the background into an MSE post, especially from papers and surveys. In the light of this observation, it is probably helpful to spend some time optimizing such answers to contain minimal information from the paper and yet summarize it while addressing the poster's question. That responsibility lies at the feet of the answerer, since they chose to write one : leaving a comment with the link and the brief explanation puts the ball in OP's court, even if the link breaks it's fine $\endgroup$ May 31, 2021 at 4:34
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    $\begingroup$ I think it is to this site's loss to delete these sort of answers, but I understand your answer. $\endgroup$
    – Holmes
    May 31, 2021 at 11:30
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    $\begingroup$ It says the answer was "Deleted and converted to a comment by Xander Henderson". I think it is reasonable to ask if this was the correct decision. I think if this answer was edited to include the proper citation to the linked article (title, journal, author + year), it should remain. It is not always practical to make an answer to a highly technical question like this "self contained", or to give a "full explanation" as requested by the OP. $\endgroup$
    – xxxxxxxxx
    Jun 2, 2021 at 5:48
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    $\begingroup$ Then the question should have been closed as too broad, and not answered at all. $\endgroup$
    – Nij
    Jun 2, 2021 at 6:45
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    $\begingroup$ @XanderHenderson Done. All I ask is that you let the community vote on whether it should be deleted. $\endgroup$
    – xxxxxxxxx
    Jun 2, 2021 at 13:47
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    $\begingroup$ @XanderHenderson why did you make such a snide remark about imaginary internet points - such a motivation doesn't apply since the OP had used something that looks like a one-time account to post the answer. But adding this insinuating remark is really distasteful, especially from a moderator... $\endgroup$
    – s.harp
    Jun 2, 2021 at 22:39
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    $\begingroup$ @XanderHenderson Your tone throughout this exchange has been pretty disappointing as a site mod to say the least. This was a very negative experience for OP who was new to the site when they were just trying to help someone out who asked a question somewhat in bad faith. Just because the content still exists doesn't mean that something wasn't lost. There is a human element to the site, and this experience may have turned OP away given that a site mod has been a bit snippy about it all, and it also creates somewhat of a precedent against directing people to papers for difficult questions. $\endgroup$ Jun 3, 2021 at 11:54
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    $\begingroup$ @XanderHenderson About nothing being lost: The answer was posted as a comment by a user only after it was deleted, the commentator presumably had nothing to do with the deletion - so something was lost by the deletion until somebody decided to recover it. Additionally an answer allows for more details and context to be given and gives more prominence than a comment. There are quite a few "reference + context" type answers on this site that are good and helpful contributions, so I think the OP has experienced some unfortunately misplaced zeal, which is usually very unpleasant. $\endgroup$
    – s.harp
    Jun 3, 2021 at 15:53
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    $\begingroup$ OK, looking more closely at the timeline I understand better - the original answer is much more suited as a comment. The current state of the answer is completely fine in my opinion, but that was not the initial state. $\endgroup$
    – s.harp
    Jun 3, 2021 at 20:33
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    $\begingroup$ @s.harp, despite claims otherwise, I think you are correct that something was lost by the initial deletion. I think Xander Henderson's comments are disingenuous at best: the answer was originally deleted and would have remained so were it not for this question, which no doubt prompted other users to take a second look and undelete it, leading eventually to it being converted to a comment etc. etc. If the original answer had simply been converted to a comment that would have made a lot more sense. $\endgroup$
    – Holmes
    Jun 3, 2021 at 20:48
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    $\begingroup$ @CameronWilliams Thanks for your kind words. I am sure if I had left my original "answer" as a comment on MO, someone would have said "why don't you give that as an answer instead". I appreciate that the websites are different, but I was just shocked that some useful mathematical information (even if not "acceptable as an answer" by this website's standards) was just deleted. $\endgroup$
    – Holmes
    Jun 3, 2021 at 20:50
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    $\begingroup$ @XanderHenderson I don't consider your comments in good faith. I don't care about my answer being accepted, I don't care about points, my question is written as a favor to (the collective) you and your website, not for me. Also, if you don't understand that new users can't post comments then I'm not sure why you are a moderator. $\endgroup$
    – Holmes
    Jun 3, 2021 at 21:06

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