My experience is that most forum style social media has been devoured into the reddit world, and furthermore that any attempt at making an offsite version of reddit or similar forum-like functionality is either locked down with rules that would make the Stasi blush or quickly converges on a new Stormfront forum.
The problem with reddit's panopticon moderation, with its ill defined, nebulously (and now AI) enforcement of sitewide policies, ends up repressing a negative behavior rather than refuting it, and, when people move to a similar off-reddit site, they are itching to start taking part in discourse they weren't allowed to before.
The end result is that people who are used to policing their own speech to avoid the panopticon rather than because it's the right thing to do eventually lose that moral code that was previously shaped by discourse and pushback from their peers rather than anonymous opaque moderation.
Repressing rather than refuting pretty closely models real life though.
Usually if you violate social norms people just push you out of the group and not bother explaining it to you. Not always, but usually. Yes if it is so bad it gets violent or something you will find out for sure why, but if you just show up to a friend function and start spouting off about gassing the jews or something most likely people just won't invite you back and never explain why.
Actually finding out why you were violating social norms I've found is mainly found either on the internet or from your parents when young. Hardly anyone in real life is going to bother telling you why, especially when some people are liable to act violently and there is no upside to them for bothering to explain it to you.
Socialization usually involves corrective action and nuance. A platform that will give you an AI issued permaban for saying "Say that again and I'll knock ur block off pal" about some silly topic makes people too aware of the repression and then it's sublimated in communities that approve of actually heinous stuff.