In MO 2.0 you get this message if there are “too many” comments:
Please avoid extended discussions in comments. Would you like to automatically move this discussion to chat?
IIRC an old meta-discussion there was no agreement on this advice. And many comments have been customary. Did opinions change? Otherwise: Would it be possible to remove this advice?
Even if that message is generated, I believe you can simply ignore it and make further comments.
To me, it seems an interesting experiment. On MSE, I am typically answering an undergraduate and have no interest in dragging the thing out. At MO level, from time to time there are questions with part answers, where an extended discussion between peers could be of benefit, actually result in something. The occasional joint article, for one thing.
I used to suggest pretty much this, years ago, using email off MO. Nobody ever did it, and some people disliked the idea over a lack of transparency. But the chat rooms would be transparent.
Part of the philosophy behind SE 2.0 is that the main site is for Questions and Answers, with very little discussion. Comments are for getting posts improved, either by pointing out errors or asking for clarification.
Of course, you guys are free to choose your own policy on this.
However, I'll just note that comments are very inefficient and annoying for real time discussion. Chat i awesome for this, and it even works well if the discussion is not realtime (people in different timezones, etc, etc). When you click that button, a new chat room is created (and IIRC populated with the previous comments). You can continue there (and invite more people into the conversation if you wish -- the chat room is open to all with >20 rep)
Comments in the SE engine have always been ephemeral, temporary notes that should result in some useful change to the post they're attached to, at which point they become obsolete. We didn't want them, and didn't have them originally. We added them because people kept using answers to post follow up commentary.
A long stream of comments is a bit of a burden for future readers searching for answers to the question that was asked. You arrive to the page, see that the question matches your own and then find this seemingly fantastic answer that appears to address all of your concerns. But wait, there's a long line of comments under it - is there something perhaps sub optimal that you're not seeing? So you read them all, many times unnecessarily.
Whenever possible, try to make sure comments either present something of lasting value, that should be consumed with the answer but don't exactly fit within it or are removed when they are no longer relevant by flagging them.
That said, it's just an automatically generated message that accompanies a system initiated flag alerting moderators that there's a protracted discussion going on in comments. It's up to the moderator to decide what to do. Sometimes chat just isn't feasible for people in disparate time zones, sometimes answers just require quite a bit of explanation. As the moderators have been informed, the system trusts that whatever action they take (or don't take) is appropriate, and that's it.
Just please try to keep future readers in mind when comments get lengthy - comments that aren't essential reading to fully understand the answer (which can usually be moved into the answer) just create unnecessary reading - and that's what we're trying to avoid.
