I periodically will try to puzzle out how to design a forum that would minimize the aggressive posters.
There is something maybe to the mechanic of hiding sub-topics or conversational tangents.
A poster states something like: "the Mankins trade is yet another idiotic move by Belichick"
A responder can opt to have his response to this quote created in a tangent sub-thread. A big plus graphic could be put at the bottom of that flammatory post with something like: This post has one reply. Or more than likely: This post has 1574 replies.
Clicking on that Plus would open up the sub-topic.. but leave it hidden to anyone that hadnt clicked on it from the main thread.
Its not perfect, but it gives posters the option of not derailing a thread if they recognize the potential of their response to do so.
I think where this mechanic fails in other forums is when a topic has dozens and dozens of mini branches that require clicking just to see a comment to a comment. I find it annoying to click on a hundred Pluses to read a back and forth.
Moderators then could be real sticklers about keeping the main/visible thread on topic and much of the back and forth could be hidden in a sub-topic.
A Thread on the main page could have an icon to represent Show Subtopics. Clicking on it and we might then see something like:
Mankins Traded!!
-Sub Topic: Re: Belichick is an idiot [1653 replies]
-Sub Topic: Re: Belichick is a genius! [2573 replies]
-Default Sub Topic Where Posters Argue Semantics [875578754 replies]
As I said this idea isnt perfect but I feel theres a real good idea/system that could come out of it.