Wasn’t IRC itself pretty much federated, just maybe not calling it that yet? Networked I think they called it. You’d have a bunch of servers in a network and users could join channels and chat with users on other networks. Every now and then you’d get a server split where some subset of servers would lose connection with the rest and a bunch of people would all leave the channel at once. Then, it would resolve, and they’d come flooding back in.
Yes. For example, you’d have a collection of servers that federated to create EFnet. DaLnet, etc. Joining any of those servers would get you onto that federated network. You could be banned from one server but you could always choose another to still get into the same network. And yes, netsplits happened. A lot.