This has just happened to one of my answers, so I thought I'd ask here whether people think it's OK.

I posted an answer to a question about physical units appearing in exponents and the like. Shortly afterwards, a whole paragraph of additional explanation appeared at the end of my answer. The editor had around 4500 reputation points.

I don't disagree at all with what the additional material says, but it's certainly new material. Good material, but an additional point beyond what I'd said.

I dealt with it by putting it in square brackets with —added by . . . to credit the source. But is inserting substantive new material into an answer this way considered appropriate? I thought we were supposed to avoid it. (In fact I nearly had an edit rejected which consisted of adding something the questioner had asked me to—he'd said it in a comment but didn't feel confident in adding it himself.)

About a third of the answer now consists of the added material.

Edit: I've now replaced the inserted material with an explanation based on it.

  • 1
    $\begingroup$ The question is math.stackexchange.com/questions/3035641/units-of-function/… . I think it may not last long though. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 20:27
  • 7
    $\begingroup$ No, that is not appropriate for edits. When such "edits" are proposed by users under 2000 rep, they are reviewed first, and such a proposed edit is usually declined (rejected). Edits should aim to deal with grammar, typos, or assisting with formatting in mathjax, if needed, but all in all, should be minor, and not add additional material not covered by the asker/answerer. This edit was inappropriate, and if the editor felt it needed to be said, the editor should have written his edit in a comment. $\endgroup$
    – amWhy
    Commented Dec 11, 2018 at 20:33
  • $\begingroup$ I've left it in because it's relevant and improves my answer, but now only ⅔ of it actually is my answer! If I edit, I'm attempting to copy-edit the material without any change from the intended meaning. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 20:37
  • $\begingroup$ Curious why you ask questions here, when you already have decided what the right answer ought to be? No matter the feedback you've gotten on a couple of your meta questions, you seem not to acknowledge it, and make up your own mind, anyway. So why did you post this question? $\endgroup$
    – amWhy
    Commented Dec 11, 2018 at 23:36
  • 1
    $\begingroup$ Uncertainty as to whether my answer was the consensus one. Your comments reassured me that I read on the right track and that I shouldn't just defer to the person who made the edit. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 23:44
  • $\begingroup$ @amwhy Sorry for all the typos. reassured me that I was on the right track $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 23:49
  • $\begingroup$ @amwhy I think also I'm reluctant to treat the questions as answered too soon—I wait in case more people have something to say, then must likely forget to come back. But I keep asking because I'm unsure that my judgement will fit what's expected on the site. I'm still very new here. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 23:57
  • $\begingroup$ timtfj All very understandable. No problem! $\endgroup$
    – amWhy
    Commented Dec 12, 2018 at 0:00
  • $\begingroup$ @amwhy I'll try to make a more obvious acknowledgement in future though. If people have helped me I want them to realise that! $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 0:02
  • $\begingroup$ @amWhy Re acknowledging replies—I've just realised that the guidance in the Help Center seems to discourage the most natural ways to do it: in particular it warns against leaving a comment thanking someone for their answer (!) and says the correct thing is to upvote/accept it instead. (Not as well: instead.) But upvotiing is anonymous so they don't get thanked. Maybe I'm interpreting the advice too rigidly / literally / legalistically. $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 2:18
  • 4
    $\begingroup$ It's probably worth mentioning that situation is rather different if the answer is community wiki. (Which is - as the name suggest - intended to be "co-owned" and maintained by the whole community.) $\endgroup$ Commented Dec 12, 2018 at 2:21
  • 1
    $\begingroup$ This seems related, although it is mainly about suggested edits: Edits that Substantially Extend Answers. $\endgroup$ Commented Dec 12, 2018 at 2:23
  • $\begingroup$ @Martin Good point. I've set a couple to CW when comments needed turning into an answer—since it was really the commenters' answer, not mine. $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 2:24
  • $\begingroup$ @Martin Yes, it's a very similar situation. (I was surprised the edit to my post wasn't rejected, then realised the editor didn't need edits to be approved.) $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 2:31
  • $\begingroup$ It is better to add a separate answer rather than modifying someone else's answer. Here is an example : math.stackexchange.com/a/2152231/72031 $\endgroup$
    – Paramanand Singh Mod
    Commented Dec 16, 2018 at 7:45

2 Answers 2


My own answer: I think the person with the new material should either

  • put it in a separate answer mentioning the first one, or
  • suggest it to the writer of the first answer, maybe offering to do the work of editing it in

but not simply edit into the answer. To my mind that's not really an edit.

Also, the author and editor might be aiming for different things. I'm often striving to avoid technical language; in this case I was trying to relate my answer to electronic engineering since that's where the questioner might have encountered a voltage appearing in an exponent. (Specifically, it happens in the equation relating current and voltage for a diode).

Edit Thanks the responses—I needed to know that I was on the right track with this.

  • 2
    $\begingroup$ The one who contributed the edit most likely thought it was constructive/helpful, but I would not insert such a block of new information in someone else's Answer unless I got their approval by way of exchanging Comments. You would have been justified in rolling back the edit, but congratulations on dealing with it in a more gracious manner. $\endgroup$
    – hardmath
    Commented Dec 11, 2018 at 20:42
  • $\begingroup$ Thanks. I'm still pretty uncomfortable about it, but I felt it made sense to leave it in. I might edit it into the version I would have written, though. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 20:46
  • $\begingroup$ And I've now done the latter. $\endgroup$
    – timtfj
    Commented Dec 11, 2018 at 22:17
  • $\begingroup$ @hardmath Im sure you're right that their intent was good. I think they mainly saw something that obviously belonged in the answer, and added it. $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 2:21
  • $\begingroup$ When I read the Question, I thought your Comment asking about the diode was a good request for clarification. While the OP there never seems to have responded, it would make a good illustration to include in your Answer, if time permits. $\endgroup$
    – hardmath
    Commented Dec 12, 2018 at 2:40
  • $\begingroup$ @hardmath It's decades since I knew the equation (I studied electronic engineering but didn't become an engineer) so I'd have to dig it out. If he's asking about voltage in the exponent he must have something like that in mind. Possibly something like quantum tunnelling of electrons out of a cathode, but I can't remember whether that's exponential wrt voltage. $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 2:56
  • $\begingroup$ Wikipedia's take on the subject is titled the Shockley diode equation. $\endgroup$
    – hardmath
    Commented Dec 12, 2018 at 3:34
  • $\begingroup$ @hardmath Thanks for that—I'll have a look and then I can at least add the link. $\endgroup$
    – timtfj
    Commented Dec 12, 2018 at 18:21
  • $\begingroup$ I agree with you. Your answer is your answer and reflects on your reputation (the real one, not the points). In a case like this I would either propose the additional material in a comment and say you are welcome to use it or write a new answer with the new material and say it is an addition to your answer. I have done both. My division is based on how extensive the addition is. $\endgroup$ Commented Dec 15, 2018 at 4:47

"I would have written a shorter letter, but I did not have the time." -- Pascal

When I answer questions on math.stackexchange, I often put a lot of effort into making my answer short and concise. (At least I aim to be concise, whether or not I succeed.) So I don't think substantial new material should be edited into an answer by another user. On the other hand, comments suggesting material to add can be very helpful.

If anyone remembers the old Google Knol project, the idea was to have something like Wikipedia but where content is attached to specific authors. I think that was a good idea, and I believe it has worked well on stackexchange and on Quora.

  • $\begingroup$ The conciseness point is important and it's also a style point: one person is aiming for self-explanatory maths with no words, another is aiming for a concise explanation of the concepts. (In the the event, I edited the inserted material beyond recognition and it ironically got longer, but I still agree with you.) $\endgroup$
    – timtfj
    Commented Dec 23, 2018 at 15:23

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