This is really interesting, one question that comes to mind is whether popular discussions will become stressful for the original two people as others create new threads off certain comments. It seems that you would either have to ignore those new threads or inevitably end up having to keep track of a potentially deeply branching, difficult to follow discussion - having to make the same points in parallel to multiple people.

Some way to fan in the conversation and allow multiple participants as points converge could solve this but it sounds like it would be rather complex to get right.