Dude, apparently unlike you, I remember Usenet, which uses precisely the sort of system you’re describing, in its heyday. That means I’ve also seen discussion groups implode because they couldn’t get rid of a single bad actor. Killfiles alone aren’t enough, even when combined with community naming-and-shaming. Someone always lacks self-restraint and engages. That encourages the bad actor(s). They post more, often using multiple sockpuppets to get around people’s killfiles and flood out legitimate discussion. Newcomers to the group see masses of bad actor spam and fail to stick around. The lack of new blood kills the group.

Self-moderation simply doesn’t work. Yes, bad moderation happens and I’ve seen plenty of examples. But no overarching moderation is also the kiss of death.