It doesn't have to be specific to private group chats. The same model worked well on public forums. The only reason it doesn't work on mainstream social media

It doesn't have to be specific to private group chats. The same model worked well on public forums. The only reason it doesn't work on mainstream social media is that "assholes" not only still "engage" with the product (and watch ads) but they also cause other people to argue with them and "engage" more, so it's actually profitable to keep them around.