usenet is similar, yea. messages sent between servers. but not much to differentiate between servers, though. different instances here have or are developing their own 'personality' or focus, which didn't really exist among usenet servers.

i think lemmy and the 'federation' is more like the old fidonet from the days of dial-up bulletin boards. posts and other content get sent between instances like echos and echomail did between bulletin boards in fidonet. each bbs was different and had different features, user bases, etc, and most had a theme or central topic of some sort. some were multiline with chat and multiplayer games (tradewars anyone?) sysops chose whether to participate in fidonet, and which echos they carried. fidonet also had netmail (a kin to email today) and networked file distribution.

Yes! The business about servers not carrying some groups but carrying others feels a lot like the Lemmy federation wars.