So I'm not sure how this would all work out, but an idea I just had might be to track who is the OP of a given thread through its entirety. This would be especially useful in, say, philosophical debates when a thread gets really long and you can't quite remember who exactly you are arguing to. Another reason I could see this being implemented would be if OP is asking for advice, I sometimes like to scan the last few pages of the thread to see if OP is still checking in/commenting on ideas. Having a tracker would make it a lot easier than having to remember to keep a tab open to the front page or having to remember OP's username.
You can find out who the OP is by middle clicking the forum section the thread is in, [size=10](which opens a new tab)[/h], and then looking for the thread topic and looking at OP's username.
As for keeping track of arguements, I'd have to agree that some threads get excessively long and quote pyramids get a bit much if you aren't involved. You get notifications when somebody quotes you, so if you're in the middle of a discussion with someone you can instantly go to the thread in one click when you receive one.