They could put virality limiters on content, for example limiting the number of times a message can be forwarded. WhatsApp is known to have done this. They coul

They could put virality limiters on content, for example limiting the number of times a message can be forwarded. WhatsApp is known to have done this. They could also let people report users (and unmask their content) and ban them if they get enough reports. They could also push out clientside hash checking of controversial content once they’ve received reports and stop it from propagating there - just get the database from GIFCT. If group membership can be seen by others in the group, they could also take reports of group membership from NGO or government observers and ban everyone in the group. One does not simply chat online.