Sorry but I see dialogues more often under the answers at Quora than I see at Branch(es?)
Quora gives your full attention to an answer. It collapses the comments. It lets you downvote unpopular opinions.
Branch limits the most that anyone can say at a time (to something like 800 characters--which is enough for an explanation but not enough for a tirade). And it gives equal weight to each comment that someone makes.