Related (possible duplicates):Dealing with answers in comments and What should one do when one's question has been answered in the comments?

I've seen this more than a couple times now: here is a question where an answer was posted in a comment, and then on the urging of another member, converted into an answer (which was subsequently upvoted and accepted). Here is another question where a fairly complete answer was posted as a comment.

Conversely, @t.b. pointed out that some things that are more appropriate as comments are posted as answers (I don't have any concrete examples on hand).

The only guidance in the FAQ seems to be that comments are appropriate for asking clarification or pointing out improvements that could be made; and that answers should be relevant and answer the question.

What are the guidelines for what should be posted as an answer and what should be posted as a comment?

  • 5
    $\begingroup$ I see the opposite problem: too many comments posted as answers. $\endgroup$
    – t.b.
    Nov 15, 2011 at 0:09
  • 4
    $\begingroup$ I just plea for some leniency. Okay, maybe I shouldn't have posted those two matrices as a comment and should have let somebody else come up with that great discovery, but if I feel like commenting I comment, and if I feel like elaborating something into an answer I'll write an answer but please, pretty please, let me decide that myself. $\endgroup$
    – t.b.
    Nov 15, 2011 at 0:23
  • $\begingroup$ @t.b. I'm certainly not making accusations or anything of that sort; your situation simply made me realize that the distinction between when partial answers should be posted as comments or answers is unclear to me, and I couldn't find any guidance to clear it up. I'd be happy to remove the reference to your answer if you'd like. $\endgroup$
    – smackcrane
    Nov 15, 2011 at 0:33
  • $\begingroup$ No, don't worry, just leave it, it's perfectly fine with me. I'll let others answer who are more insistent on that point than I am. $\endgroup$
    – t.b.
    Nov 15, 2011 at 0:46
  • 1
    $\begingroup$ Related (or perhaps dupe): meta.math.stackexchange.com/questions/1559/… $\endgroup$
    – Aryabhata
    Nov 15, 2011 at 1:08
  • $\begingroup$ @Aryabhata thanks, that question is dealing with essentially the same problem, but a slightly different question ... I'll leave it to others to decide if it's a duplicate. $\endgroup$
    – smackcrane
    Nov 15, 2011 at 2:01
  • 1
    $\begingroup$ @t.b. The fact that I want answered questions not turning up in the unanswered tab does not mean that I have any interest in answering a question that you or anyone else have already answered in the comments, quite the opposite, which is the reason that I don't want it to look unanswered in the first place. $\endgroup$
    – Phira
    Nov 15, 2011 at 8:36

1 Answer 1


Despite this having been discussed multiple times:

What are the guidelines for what should be posted as an answer and what should be posted as a comment?

There should be none. Like most other things in a community forum, it is up to the users to make their own best judgements. In this case, @t.b. didn't think what he wrote deserved to be an answer, but doesn't hold that position strongly. So when poked by @Listings about it, he changed his mind. (I actually wrote the exactly the same comment as t.b. did for that question, with a poke to @sos440 to post his/her comment as an answer; I deleted that after seeing t.b. had me beaten by seconds).

<rant on cultural norms> It is generally in the culture of Mathematicians to be more conservative about what they say: they tend to be more cautious about unqualified statements (c.f. that joke with engineer, physicist, and mathematician ending with "...there's at least one sheep in Scotland of which at least one of its sides is black"). This also leads to a lot of mathematicians snarking at physics journals publishing what they consider to be "easy corollaries of known results". This self-set high bar for what is publication-worthy may or may not have something to do with how a lot of partial answers appear as comments in this website. </rant on cultural norms>

Another possibility, besides my above rant, is that the user is only leaving a short sketch of the complete answer in the comments. For those with sufficient mathematical maturity, those short sketches may appear to be a complete answer. But for a self-conscious educator, those sketches may not be sufficiently pedagogical as an answer. Nobody, not even the great @Arturo Magidin himself can write Arturo-style expositions for every question seen. (In your second link, I would assert that by Arturo's standards, that comment is far from a complete answer...)

On the flip side, because of the Q&A (emphasis on the A part) nature of this site, we desire answers. So if a user decides to post an answer as a comment, I think he or she should not complain when somebody else decides to incorporate the content of said comment into a "more complete" answer.

Which leads to...

If you see an "unanswered question" with the answer already appearing in the comments, you can either:

  • Ping the author of that comment and request that it be posted as an answer;
  • Just copy the comment and post it as an answer yourself (perhaps with proper attribution, and/or marking it as community wiki if you don't want the credit); or
  • Expand upon that comment and write a better, clearer answer.

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