What triggered this post is this question, which has two quality answers but due to some contested points, both have spurred lengthy discussions in comments from a few users.
Now, I have no problem with the users here - I think the comments there are all relevant and on-topic - but I do think that these sort of discussions generally do not belong as comments, and I think the community will agree (downvote me if you disagree!).
Now, comments are useful for pointing out things the poster perceives as mistakes, inaccuracies or missing information, which is the case in those answers; but the back-and-forth cycle does not really belong there. When a new user comes to look at the question he isn't interested in reading a discussion about the answers, but just getting answers - that's the whole point behind SE engine. And the amount of agreement every answer enjoys is expressed well enough in votes.
All this is especially true now that we have a chat available, which is precisely the place for those discussions.
So the question here is whether you agree with me that we should actively discourage extended discussion in comments, and if you agree, how should we do it?
For example we could add a line about it in our FAQ, then enforce it somehow.