Can a user be banned on their host instance for breaking the host's rules on other instances?

As I understand it, Lemmy is a place for discussing concepts under a general umbrella. Maybe make a c/micropenis to see if there's enough traction, then a server could make sense where you can set the rules. But those post won't be available across Lemmy if that's your desire. This being the case, and for anything nudity related, it'd be safe to assume there's plenty of space in the Fediverse for it, just not here.