There is also (or at least there was before my account was moderatorized) a button on the comment section to automatically move your discussion to chat. When you see it, this is a very strong hint. Take it.
Pretty much any time you feel the desire to add a third or forth in a series of back-and-forth comments between two people, you really need to either let it slide, or take it to chat. If any resolution is agreed upon in the chat, that can go in a comment, but otherwise you are really just making the item's comments less useful, not more.
UPDATE
Backing IHTK up here. This has really started to get out of hand again in the last few days.
Just this morning I cleared a auto-generated flag on an otherwise good user account (@Anixx just so he knows) because he'd created more than 20 comments in the last couple of days.
He's far from the only culprit though. Everybody please consider the value you are adding to the question (or answer) you are commenting on before commenting. If you want to discuss a disagreement over a point, please take it to chat.
Hopefully everybody just has a touch of spring fever, and this will all blow over in a couple of weeks...