Yeah, each node operator maintains his own instance. The idea of federation is that the user space is voluntarily split up enough between nodes that moderation

Yeah, each node operator maintains his own instance. The idea of federation is that the user space is voluntarily split up enough between nodes that moderation can be handled by one or two individuals, unlike a Facebook or Instagram which needs an army of contractor labor and exotic algorithms to do the same thing. If you're trying to stop the propogation of "Bad Stuff" overall that battle has been pretty much lost with the invention of onion routing (or more likely encryption) so now it's just damage mitigation, in which case see above