Wouldn't that strengthen the echo-chamber effect? If the original poster supports position X and does not allow anyone who supports position Y in to the convers

Wouldn't that strengthen the echo-chamber effect? If the original poster supports position X and does not allow anyone who supports position Y in to the conversation, then a position Y person will eventually start another thread and not allow anyone from position X to reply. So now you have two threads: one for position X supporters and one for position Y supporters, with no cross-talk between the two. Unless, of course, there's some kind of mechanism that gives threads with higher engagement more prominence? That might create an incentive to have more inclusive conversations. Although that might incentivise trolling too... EDIT: Perhaps combine the above with a reputation system, where you can see how ban-happy an original poster is. Since people don't like to waste their effort writing a reply that just gets ignored, ban-happy posters would be penalised by lack of engagement. Then platform provided moderation could just become a kind of 'meta-moderation' - basically just banning people who try to game the system (e.g. posting threads saying 'please reply so I can get my ban percentage down').