Also in practice the sentences come out a bit unclear to me. “The fed that posted this clearly knew their stuff.” “Some feds just like to stir things up.”
Edit: that said, I think that’s a really good point about the need for a platform neutral term.
Mastodonians, Kbingers, and Fedizens are all superb. I’m not a fan of “feds” because it has another pretty common usage. I feel like whatever term is chosen should unambiguously evoke the fediverse.
Depends a little on what instance you're from. For example people from the one I'm on are sh.itheads. Besides that I've heard lemmings for lemmy and fedizens for the greater fediverse a lot. I've also heard karabiner for kbin users.