The SE universe has a "comments are not for extended discussion" policy, with the effect that if such an extended discussion occurs, moderators intervene and "move the discussion to chat".

I am a user that does not use chat -meaning that such a movement effectively kills the discussion for me. So I have the motive to ask:

"What are the evidence-based arguments in favor of this policy?"

I personally see none. I stress that "general logical/plausible arguments" are useless after all these years. They may have been useful in the beginning of the SE universe, but not anymore. Is there any evidence that extended discussions in comments lower the quality of the SE sites content? Is there any evidence that they confuse users? And is there any evidence specific to CV?

There is certainly evidence that the policy disrupts useful accumulation of knowledge and pisses users off. Where is this evidence? It currently writes this post.

PS: I used also the tug "bug" because this is "an erroneous behavior in the system that needs to be fixed" (the human system in this instance).

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    $\begingroup$ I can't accept most of your premises. This is behavior by design. Comments are to solicit clarifications of questions and answers, not for discussion. They automatically are of lower quality than answers because they are not voted on or accepted. IMHO, comments would be better off if they automatically disappeared after a reasonable period, such as a month, because so many of them are junk. I'm having a hard time with the characterization that they are "useful accumulation of knowledge." Accumulate the knowledge in appropriate answers. $\endgroup$ – whuber Nov 5 '18 at 21:39
  • $\begingroup$ I apologize but this is not reporting a bug in the SE software so I removed the tag [bug] even though I appreciated your joke on human system. (I can also sympathize with your feelings to some extent.) $\endgroup$ – amoeba Nov 5 '18 at 21:46
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    $\begingroup$ @whuber These are not premises, but observed regularities. Bits of useful knowledge come up in comments, useful clarifications come up in comments, clever ideas come up in comments, and these cannot be turned into answers. Sometimes they don't have anything to do with "what the OP asks." So what? By persecuting comments we lose all that. So it comes down to cost-benefit analysis: what is the harm done by comments? $\endgroup$ – Alecos Papadopoulos Nov 5 '18 at 22:21
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    $\begingroup$ @AlecosPapadopoulos by design comments are second-class citizens in here: they are not voted, they are short, can be easily deleted, are made less visible then answers. If comments have meaningful and helpful parts, they should e included in answers. There is no open-access data on this, but I guess that most people won't even look at the comments, so they shouldn't be promoted anyhow. $\endgroup$ – Tim Nov 5 '18 at 22:40
  • $\begingroup$ @Tim ...and as is quite often the case in general, "second-class" citizens occasionally are more interesting than the first-class. And again, not everything useful and inspiring in comments can or should be made into an answer. $\endgroup$ – Alecos Papadopoulos Nov 5 '18 at 22:45
  • $\begingroup$ I doubt that this is being denied, but there is voting on comments in this sense: you can add your +1 to a comment you like. (I've often wanted to subtract 1 from a comment I didn't like, but perhaps it really is well that isn't on offer.) $\endgroup$ – Nick Cox Nov 9 '18 at 17:48

What is the actual harm done by an extended discussion in the comments?

  1. An extended discussion in the comments obscures any other comments that do not belong to this discussion. Simply because they become hard to spot. Only 5 comments are visible without "expanding"; if there are 25 comments of a discussion between users @A and @B, then very few people will ever see a 26th comment by @C that might contain important criticism of the answer, or an important insight. Worse, @A and @B might go on to post another 25 comments after @C's one, in which case it is practically guaranteed that nobody else will ever see it.

  2. Extended discussions in the comments tend to escalate. Yes, I can imagine a civil and interesting "extended discussion" in the comments, but very often they get ugly. Even if nobody ends up raising their voice, at least one of the parties will often feel offended. SE wants to prevent this from happening by stating that it is not a platform for debates.

If a discussion is ongoing, appears meaningful and remains civil, then I prefer moderators to let it go for some time before eventually moving the whole thing to chat when it's over anyway. However, if it starts to lose civility, I think it makes sense to move it away asap. That might have been the case for the discussion that has triggered this thread.


This is more of a comment but it grew over-long.

If the question is "why should such a policy exist", I can only say it's part of the original site design (so I guess, ask Jeff Atwood and Joel Spolsky what their reasons were and what evidence they might have considered for making it that way, though they have written a number of posts that give some hint of what things they were trying to avoid building - on their personal blogs, in the stackoverflow blog in 2008 and 2009, and in other places) and that a network-wide policy discussion probably belongs on the network meta.

Edit: Alecos has explained that the remainder is not relevant to the intended question. I'll leave it here for the present, however.

If the question is "does a formal policy exist" you can find numerous references to such a policy. For example

  1. In relation to the present instance, see https://stats.stackexchange.com/help/privileges/comment see especially "When shouldn't I comment?", in particular the item, "Secondary discussion or debating a controversial point".

  2. The FAQ, specifically How do comments work? - particularly "when should comments be deleted?" and "Miscellaneous information" in the answer

But before we even need to go and find these specific words elsewhere, the fact that Stack Exchange got someone to code a tool to auto-move messages to chat and which posts that not-for-extended-discussion comment itself suggests that it is official policy to do so (why would they spend money to provide mods on every site on the network with a tool to do something that was not a mod behavior they considered important behavior to encourage?)

While we're more tolerant on SE of informative comments that are not-quite-answers on our site than many other network sites (it's part of the nature of the topic, I think, though you see it to some extent on math.SE and mathoverflow for example), nevertheless comments are primarily designed for improving a post and in that role, are generally intended to be temporary.

Extended discussion formally belongs on chat, by design.

  • $\begingroup$ This answer, together with the comments on the OP's post, re-iterates "this is the policy". It is obvious that I challenge the wisdom of the policy. $\endgroup$ – Alecos Papadopoulos Nov 5 '18 at 23:02
  • $\begingroup$ HI Alecos; it occurred to me just after I posted that I may have misunderstood your question. I have addressed this above $\endgroup$ – Glen_b Nov 5 '18 at 23:05
  • $\begingroup$ Indeed, thanks for adjusting your post. The issue for me is "now that there are years of accumulated experience, I do not see the justification of keeping this policy". $\endgroup$ – Alecos Papadopoulos Nov 5 '18 at 23:08

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