Due to recent questions about the comment policy, and because I have seen this being done often, I am here with another question about comments.

On a certain question a user commented

A primary purpose of comments on this site is to point out erroneous assumptions in questions, in order to help the OP to improve them.

Of course the goal is valid: comments should be used to help the OP improve the question. But is this a general principle? Should content that points out errors with the OP's logic/understanding be posted as a comment or as an answer? If such a comment is valid, then what should be the goal of the comment?


I'll pick on your last two sentences, if I may:

Should content that points out errors with the OP's logic/understanding be posted as a comment or as an answer?

The ultimate guideline for these things (as far as I'm concerned):

  1. If it answers the question, it should be posted as an answer
  2. Otherwise, if it explicitly or implicitly suggests a change to the question, it should be posted as a comment
  3. Otherwise, it probably should not be posted at all

Granted, that's still somewhat ambiguous, but all the ambiguity is in the meaning of "answers the question" and "suggests a change to the question".

There are some cases where an OP makes an erroneous assumption and correcting that assumption actually answers their question. In those cases, you'd post an answer, not a comment. For example, if a question takes the form "I want to X but can't because Y; how can I X?" where it turns out that Y isn't true, then posting that Y isn't true and the OP actually can X the way they wanted to is a perfectly legitimate answer.

In other cases, correcting the OP's erroneous assumption doesn't actually answer the question, and in those cases you'd leave a comment. Even just pointing it out is enough - if you bring the OP's attention to an error in their question, that's the sort of thing I consider an "implicit suggestion" to make a change.

If such a comment is valid, then what should be the goal of the comment?

I think the goal is to get the OP to rewrite the question in a way that doesn't include their erroneous assumptions. That falls under suggesting a change to the question, so it's a legitimate comment.

  • $\begingroup$ Thanks for the input. I agree with all of it. $\endgroup$ Aug 4 '20 at 20:09

As the person whose comment triggered the question, I would like to say that I agree with everything David Z wrote, but not with everything that BioPhysicist wrote.

My understanding of this site is that it is the responsibility of the OP — and no one else — to write a good question. They are rewarded for doing so and penalized for writing a bad one. The purpose of a comment pointing out a flaw in the OP’s thinking is to get the OP to figure out how to improve the question. A commenter should not be expected to make any suggestion about how to improve it. It’s great if someone chooses to do that, but it shouldn’t become an expectation.

If it becomes the policy that I must suggest improvements to the OP when I point out an error, then I will simply stop pointing out errors. Then more errors will likely go unchallenged, leading to readers getting incorrect ideas about physics.

I am happy to answer good questions, but I am not happy to be expected to have to suggest how to improve the poor ones just because I want to point out their flaws in a comment intended to be helpful both to readers and to the OP.

  • $\begingroup$ I don't think anyone is expected to tell the OP how to improve a post. But if you are making a comment then that is what the comment should do. IMO it isn't always obvious how an actual question will be improved by just pointing out flawed assumptions, especially for the OP who is obviously already confused. And sometimes pointing out flawed assumptions isn't even a call to improve the question. But there are various scenarios and that is what I tried to cover in my answer here. $\endgroup$ Aug 4 '20 at 21:40
  • $\begingroup$ Also, I don't see much difference between my answer and David's. Can you elaborate on that more? $\endgroup$ Aug 4 '20 at 21:43
  • 2
    $\begingroup$ @BioPhysicist DavidZ didn’t say anything about guiding the OP to improve the question like you did. I consider simply pointing out errors to be sufficient “guidance”. I’ve indicated that the question has a flawed assumption. Figuring out how to improve it is solely the OP’s responsibility. Sometimes an appropriate response is deletion. $\endgroup$
    – G. Smith
    Aug 4 '20 at 21:50
  • $\begingroup$ Yeah, I guess the word "guide" might be too strong. I changed it to "help". IMO adding a little more to a comment isn't a huge burden, but it seems like just a difference of opinion at this point. Thanks for the chat. $\endgroup$ Aug 4 '20 at 21:58
  • $\begingroup$ Sorry, it wasn't my intention to call anyone out. My post said nothing about the question's quality. I was merely wanting to discuss the comment policy. I have removed the link. I didn't mean to offend you, and I wasn't trying to suggest anything against you. I was just giving context to an idea I see a lot on the site and wanted to ask about. $\endgroup$ Aug 4 '20 at 22:02
  • $\begingroup$ @BioPhysicist I understand your point of view and I am not offended. But I want to understand what the policy is going to be. I will pay attention to the votes on the answers, especially if mine is highly downvoted, but will not necessarily change what I’ve been doing for the last two years unless asked to do so by a moderator. $\endgroup$
    – G. Smith
    Aug 4 '20 at 22:05
  • $\begingroup$ I think it is more of an interpretation. If you think that just pointing out the flaw is a suggestion for improving the question itself, then you would be following the policy. At this point I think it is just splitting hairs though. But what else can us high-rep users discuss? ;) $\endgroup$ Aug 4 '20 at 22:08
  • 2
    $\begingroup$ I definitely think that just pointing out a flaw in someone’s reasoning is helping them to realize that their question needs improvement. I think we’ve said enough. $\endgroup$
    – G. Smith
    Aug 4 '20 at 22:11
  • $\begingroup$ While constructive critisism would be better, you could add a canned phrase to the effect of "At the moment I am not in a position to provide a suggestion/solution." $\endgroup$ Aug 5 '20 at 10:28
  • 1
    $\begingroup$ I would argue that your concern about points is misguided. They don't have any actual value. They're just numbers which, due to a quirk of our brains, help motivate us, like scores in a game. The goal is just to make a good Q&A site--which means having good questions and good answers. Hence the comments--you're helping improve the Question (or Answer). The points they may get for doing so aren't payment, just motivation to improve the Answer. No one deserves any points, and points don't demonstrate equal knowledge or effort. They're just numbers. $\endgroup$
    – trlkly
    Aug 15 '20 at 3:00
  • $\begingroup$ If you don't think that way, then people who got here sooner and got the easier questions and answers, or people who have the good luck of picking a popular question--all of them have unfairly too many points, and keep getting more points with no extra effort. You can't think of points as something with value, with money, or the whole system just rewards the rich. (This is also why someone having a lot of points means nothing in whether they should get deference. Some complete newbie can come in and have the better Question, Answer, idea, etc.) $\endgroup$
    – trlkly
    Aug 15 '20 at 3:04
  • 2
    $\begingroup$ FWIW I totally agree that comments shouldn't be required to actually suggest a specific change the OP should make to their post. Pointing out an error or a flawed underlying assumption is a totally valid use of a comment (of course as long as it doesn't constitute an answer :-p). $\endgroup$
    – David Z
    Aug 16 '20 at 3:10
  • $\begingroup$ Also @trlkly well said in your first comment there. $\endgroup$
    – David Z
    Aug 16 '20 at 3:11
  • $\begingroup$ @DavidZ The issue I have sometimes is that "pointing out an error or a flawed underlying assumption" doesn't necessarily tie into improving the post itself. Most of the comments I see doing this would just be better off as answers since pointing out these flaws is usually what is needed to resolve the question. Of course it shouldn't be expected to completely outline to a user how to improve a post, but at the same time when I see comments that only point out flawed understanding, etc. I often fail to see what improvements the commenter really thinks should be made to the question itself. $\endgroup$ Aug 16 '20 at 3:53
  • $\begingroup$ @BioPhysicist Hm, I don't think my experience upholds that pointing out those flaws is usually what is needed to resolve the question. Sometimes it is, yes, but I think those cases are a minority. Also, I think your wording might give the wrong impression, when you say "would just be better off as answers". Those comments absolutely should not have been posted as comments in the first place, if they are answering the question. And finally, if you don't see what improvements the commenter thinks should be made, that's fine; an OP in your position can always just ignore the comment. $\endgroup$
    – David Z
    Aug 16 '20 at 5:03

I suppose there are different scenarios where this could be applicable:

  1. The invalid assumptions are not a key point in the question, and they would not really need to be addressed in an answer to sufficiently answer the question.

  2. The invalid assumptions are a key point in the question, and so they would need to be addressed in an answer to sufficiently answer the question. Pointing out the flaw in the reasoning might actually be the answer the OP is looking for, even if they weren't explicitly asking about flaws in their assumptions.

  3. The invalid assumptions are making the question unclear, so making an answer is not possible. But if the invalid assumptions were cleared up then an answer could be made.

  4. The invalid assumptions make the question incoherent, and it is hard to know where to even begin in correcting/answering the question. Pointing out the flaws won't really answer the question. Instead it will make the entire question invalid (IMO the question linked to above falls into this category).

IMO the correct response to these are to

  1. Post an answer. If possible point out the invalid assumptions and how to correct them.
  2. Post an answer addressing the invalid assumptions.
  3. Post a comment. The comment should both/either ask the OP to clarify the flawed assumption being made and/or suggest to the OP how they can edit their question to better explain, clarify, etc. their assumptions. Depending on the severity of the flaws, vote to close also.
  4. Either attempt an answer addressing the invalid assumptions, or flag/vote the question to be closed.

As you can see above, the only instance where I think a comment is valid is instance $3$. This is because this is the only time when a user cannot really do anything else with the question, but clarification can give rise to good answers on the question.

However, in all of the cases, I do not think a comment should be used just to point out invalid assumptions. Comments like these don't explicitly call for improving the question. If you want to correct invalid assumptions, then just post an answer. If you want to help the OP to improve the question, then post a helpful comment doing so. Something like

I am confused about this assumption, can you explain more about why you think this?


You haven't stated what you are assuming about this. It would help others make an answer if you elaborated on this point.

could be good comments to make.

  • $\begingroup$ In situation 3 I would also strongly suggest flagging/voting to close. That's a big part of what the "needs more detail" close reason (formerly known as "unclear what you're asking") is there for. $\endgroup$
    – David Z
    Aug 4 '20 at 19:22
  • $\begingroup$ @DavidZ Thanks. I have added that in. $\endgroup$ Aug 4 '20 at 20:11

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