I've noticed several posts (like this question) lately that are extremely simple questions. In this question, the OP asked for an explanation as well as some examples. At the time of this writing, the accepted answer only has 21 votes while a comment on the question has 31.

The answer provides both an explanation and an illustrated example while the comment only provides an example (granted a good one).

My question is, when should simple questions be given answers like this in the comments? My understanding is that answers should never be given in the comments but here is a fairly popular question (near 2k views) where a commenter was more rewarded than an answer. Any clarification would be great!

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    $\begingroup$ Technically, comment votes are not really a reward, so ACuriousMind received nothing for that whereas JohnRennie got 210+15 points as reward. $\endgroup$ – Kyle Kanos Jul 15 '14 at 18:33
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    $\begingroup$ Strictly speaking, one should never answer a question in a comment. $\endgroup$ – ACuriousMind Jul 15 '14 at 18:47
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    $\begingroup$ One reason why I would comment over answer is because I'm not fully answering the question. In this example, the comment did not provide everything the OP asked for, but still useful information. There are other examples, but since this is a comment, I will not fully answer your question. $\endgroup$ – David Starkey Jul 16 '14 at 21:34
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    $\begingroup$ @ACuriousMind: I see what you did there :P $\endgroup$ – Nick Stauner Jul 22 '14 at 1:17
  • $\begingroup$ The comment may have more votes just because it was made earlier and had time to collect votes, and there was no answer competing during that time. $\endgroup$ – Volker Siegel Jul 23 '14 at 16:22

when should simple questions be given answers like this in the comments?


For at least two reasons: comments can be (and often are) deleted, and comments can't be downvoted, so our ability to deal with wrong information in comments is limited.

Of course, this is not something we moderators enforce too aggressively, because if someone posts a good answer as a comment, they miss out on all the reputation they could get from upvotes on that answer. So, in the short term at least, they're mostly "hurting" themselves.

If you see that someone else has posted something in a comment which should be an answer, the polite thing to do is post a comment in reply saying

@[user] that should probably be an answer

or similar. But you're not obligated to do so, and in fact you are allowed to take their comment and post it as your own answer, in which case you get the reputation. Just make sure to attribute it (e.g. "As [user] said in a comment,") and use a quote block if needed.

In this particular case, I'm not actually so sure the comment should have been an answer. It offered an example where the question really wanted an explanation.

  • $\begingroup$ Yes, but if ACuriousMind chose to answer, he would have built on that example and constructed an explanation as well. Then, it really becomes a question of sprinting (for who posts first). $\endgroup$ – 299792458 Jul 16 '14 at 6:14
  • $\begingroup$ @New_new_newbie: The "sprint" is known as the "Fastest Gun in the West" problem on MSE. Sometimes it's not worth it to the commenter, who may only wish to point the OP and others in the right direction, not to actually finish the race. $\endgroup$ – Nick Stauner Jul 22 '14 at 1:20
  • $\begingroup$ @NickStauner - You are right. But what I meant was, when we get a question on Physics.SE that we can easily answer, we jump on it - sometimes even multiple people at once! I've had that experience, e.g. see my comments here. $\endgroup$ – 299792458 Jul 22 '14 at 6:09

With elementary questions it's sometimes hard to know whether to answer the question or whether to vote to close it on the grounds that 30 seconds Googling will find the answer. In such cases I find myself between two stools. I don't want to criticise because I don't want to discourage a beginner who may be genuinely interested. However an answer would appear to encourage/reward a question that I think really shouldn't have been asked in the first place. In those circumstances I tend to provide a brief answer in a comment as a compromise - there is an extent to which answering in a comment is a thinly veiled criticism.

The question you cite will seem blindingly obvious to any working physicist, and I suspect that by answering in a comment ACuriousMind is expressing some degree of contempt for a question that really shouldn't have been asked. I don't mean this as a criticism of ACuriousMind because I very nearly did the same, and indeed 34 (at the time of writing this) other site members agree with him.

In the end I decided to answer, and the answer turned out to be vastly more popular than I expected and indeed vastly more popular than my answer merits. Oh well, the 26 upvotes are especially welcome since I discovered you could exchange SE points for Air Miles :-)

  • $\begingroup$ Say what about air miles!? That puts a whole new light on this thing. Also, "between two stools"? Never heard that one before. +1 $\endgroup$ – Jim Jul 16 '14 at 13:06
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    $\begingroup$ Whatever light this may shed on me, you are spot on regarding my personal motives for commenting instead of answering there. (Note that my above answering in a comment is just intended to be some self-referential humor) $\endgroup$ – ACuriousMind Jul 16 '14 at 13:17
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    $\begingroup$ @Jim: I have a weakness for the odder bits of English idiom, especially when they have a entertainingly puerile alternative interpretation. P.S. I probably shouldn't have said anything about the air miles until the beta programme finishes :-) $\endgroup$ – John Rennie Jul 16 '14 at 14:34
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    $\begingroup$ Ironically air miles are less useful than reputation to me :-P anyway... as far as I'm concerned, the fact that the question has an obvious answer to a working physicist is not itself a problem. This is what I mean when I say we have no level restrictions. Now, if the answer is easily found by Googling or checking Wikipedia etc., that is a problem. $\endgroup$ – David Z Jul 16 '14 at 14:41

Strictly speaking, one should never answer a question in a comment.

A counterexample: My comment on this question.

I know the answer is lurking somewhere in the Gauss planetary equations, Lagrange planetary equations, Delauney planetary equations, or Hill planetary equations. But where, and in which ones?

I also know that teasing out an answer from those planetary equations can be a nightmarish time drain. I just don't want to take the time to do it for this specific question. Maybe my comment pushed the questioner in the right direction. At the very least, my comment gave him terms to search for with his preferred search engine. On the other hand, maybe my comment didn't do a thing. It certainly was not an answer to the question.

  • $\begingroup$ In your comment you said it wasn't really an answer and I think that is the purpose of comments. You didn't give a full answer but you pushed to OP in a direction to solve their problem. $\endgroup$ – jkeuhlen Jul 23 '14 at 15:10
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    $\begingroup$ @jkeuhlen - That was exactly the intent. My comment wasn't even close to being an "answer". On the other hand, if steveOw has not read about those various planetary equations, my comment might have been enough to push him in the right direction. I suspect that the non-conservative nature of steveOw's force makes the only answer lie in numerical integration. That's just my "feel" for his question. I do know that those planetary equations provide an alternative way of doing those numerical integrations. $\endgroup$ – David Hammen Jul 23 '14 at 17:26
  • $\begingroup$ Suppose someone else other than the OP wants to expand my comment into an answer. That's perfectly fine with me. I was being lazy, that other person was being diligent. $\endgroup$ – David Hammen Jul 23 '14 at 17:34

Most people will tell you that you should never leave an answer as a comment. What they mean is if you know the answer, don't simply leave it as a comment. That I can agree with. However, what often happens (and something I am certainly guilty of) is that users aren't entirely sure of the correct answer or if the answer they think is complete. Additionally, someone may know the answer but not have references or further information to back it up and explain it. In these cases, users might leave a comment containing the gist of what they think the answer is in the hopes that it will help someone who either knows more, has more time, or has the additional insight needed to answer the question.

In some cases, one user's comment can start a comments discussion where the correct answer is eventually arrived at and agreed upon. In these cases, it usually starts as someone posting a comment answer or the like without having all the insight into the problem they feel is necessary to form an answer.

In short, if you know the answer, write an answer. If you partially know an answer (but not sure or informed enough to have faith in it as a posted answer) or think you know something that someone else could build off of or could help another answerer, then write a comment. That way you can be corrected without penalty if you're wrong or you could help to make a future answer better if you're right.

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    $\begingroup$ True, although I'd go a little stronger than that - I think partial answers should often be posted as answers, not comments. It is a gray area. Of course, one must keep in mind that posting any sort of answer, partial answer, hint, etc. in a comment puts it out there for anyone else to use and incorporate in their own answer. $\endgroup$ – David Z Jul 16 '14 at 3:36
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    $\begingroup$ @DavidZ I can't speak for others, but most of the time I will leave a partial answer in the comments with the intention that someone could use it to make a better answer than I could $\endgroup$ – Jim Jul 16 '14 at 13:03
  • $\begingroup$ I have sometimes left "an answer I am not sure about" with a clear note stating that I think my answer has problems A, B or C but might push others in the right direction. If you need a lot of words or equations, it's easier to write as an answer. As for "penalty" - you can always delete your answer (there is a small penalty related to deleted answer count, but I don't worry about those). My initial answer to the "mass of a coin" question fell into that category - I knew dimensional analysis was the way to go, but had an error. I chose to post the erroneous analysis to start the conversation. $\endgroup$ – Floris Jul 28 '14 at 19:46

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