Gregory's Serverit when demanding that their users behaved, and providers could also usually directly tie a Usenet post to a specific, identifiable person -- a particular student or employee, or a particular customer.
Even so, the system eventually failed.
Still, I'm not sure a federated, decenteralised system can work at all without, at some level, the idea that "if you don't make your users play nice, we're not going to play with you at all."