The question Find $\nabla f(x,y)$, where $f(x,y)=10x^3-5x^2+5xy+5y^2+8$ is pretty much of a kind "please, check if I did this correctly". I have clarified a couple of confusions in comments, and after the were resolved, I have told the OP that he was correct in his solution. As he mentioned that that was exactly what he wanted to know, I just posted an answer that comments were sufficient to the OP. My reasoning: not much is to be done with this question, and it should not distract the MSE people with the lack of answer. I do recall a couple of years ago a crusade to provide such answers to questions that were answered in comments, just in order to make them complete.

Instead, my answer was downvoted and closed. To quote @amWhy, do not take claim for answering a question (by posting in an answer field) what you fail to support, which to me does not sound friendly at all, and more like borderline offensive. I honestly do not get this policy.

• what you fail to support I don't understand that. I can't see your solution so I don't have any idea either. I can only hope that your answer was not like one of these : 1 , 2 Jul 23 '20 at 10:17
• I have put the comments into your (now deleted) answer - to make it easier for you to copy-paste in case you decide to create an answer from some of the stuff posted in the comments. I will also point out that in your meta question you have linked to the answer rather than to the question - I am not sure whether it was intentional. Jul 23 '20 at 10:18
• One solution I sometimes use (though probably not often enough) is to post the answer as "Community". That has the virtue of allowing the question to be marked as Answered (a virtue which a comment of the form "Yes, this is correct." lacks) and it sidesteps the implication (however unwarranted) that you seek reputational gain by posting a mechanical answer.
– lulu
Jul 23 '20 at 10:34
• I have answered that question (Had I saw @MartinSleziak 's comment earlier above I would not do that). I think there is some values in answering that question (beside removing it from the un-answered list): Some Cal 1 students fail to understand that $f'(1)$ is just the derivative at $x=1$. Some thought that they should first put $x=1$ in $f$ than differentiate (which give them $0$). Jul 23 '20 at 11:03
• (That is, I agree with the other two sentences of amWhy's comment: "You really need to say more than what you said to make this post count as an answer. Even the comments, which were posted as comments say more than what you say here.") Jul 23 '20 at 11:58
• For those who cannot access the answer, the answer stated this and only this: "You have done it correctly, explained in the comments." (postmortex, @UmbQbify, Ilya). Jul 23 '20 at 16:27
• @MartinSleziak Those sorts of edits should be done by the answerer, not by you coaching and enabling them. The comments are already on the same post for the answerer to copy and paste. Jul 23 '20 at 16:40
• @Martin Let users who can see the answer, at the time of its deletion, judge for themselves, as is, without your embellishments. And I copied and pasted the entire answer in the comment I left before the last one I left. Jul 23 '20 at 16:41
• Point of permanence of answers in contrast to comments is interesting, I was not aware of that. Especially taking into account that my comments were not deleted, whereas the answer was. For some time already I don’t care about reputation here, but why would I post the answer as community wiki if it was me who resolved OP’s questions? Finally, if something in my actions was in line with current community policies, I would have appreciated a comment clarifying it, not deletion supported with bold claims. Have not answered questions here for a while, and honestly don’t feel encouraged now either.
– Ilya
Jul 23 '20 at 23:55
• I also wonder. There are 3 downvotes to this question. What are they supposed to mean, besides the fact that downvoters simply did not like the question.
– Ilya
Jul 24 '20 at 14:53

An answer should answer the question, and so the comment from review is correct:

"This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review"

Another reason for summarising the comments in your answer is that comments are not meant to be permanent (they can be deleted), while answers are permanent (in the sense that they can always be viewed, even when they are deleted, by those with enough reputation points).

Finally, only a positive-score or accepted answer lifts a question out of the unanswered question queue*. So your answer needs to be of sufficient quality to receive upvotes. (This actually suggests another way: ask the OP to write up an answer. This helps them verify whether or not they are understanding everything correctly, and moreover you can upvote it, which will lift the question out of the unanswered question queue.)

*This is easily verified by looking at the list itself, and more details can be found in the tag-info for the unanswered-questions tag (thanks Martin for pointing this out).

• Excellent answer, and thorough. Thanks for posting it! Jul 23 '20 at 16:52
• I totally agree with this answer. Efforts should be made while an writing answer. One may even copy-paste THEIR (useful) comments while writing the answer(or quote other's). @amWhy, Thanks for letting me know. Jul 23 '20 at 16:53
• Adding guidelines for writing an answer should be helpful. (And the discussion should have ended by that) Jul 23 '20 at 16:54
• I have another question: as the OP mentioned some campaign(?) Just to make a question complete, can I(or anyone) write an answer to an old question quoting the comments of somone else? Is that "legal"? Jul 23 '20 at 17:03
• Re: only an upvoted answer - you probably meant to say "upvoted or accepted". Some sources can be found in the tag-info for the unanswered-questions tag. Jul 23 '20 at 17:18
• "...comments are not meant to be permanent..." This. A thousand times, this. And an even stronger statement applies: comments are meant to be deleted. From the point of view of the original design of the site, comments were meant to help askers (and answerers) to clarify their posts. Once the post has been edited to incorporate the suggested changes, comments are meant to be deleted (hence the "no longer needed" flag).
– Xander Henderson Mod
Jul 23 '20 at 17:58