Yeah, moderators of a community can only ban you from that community, server admins can only ban you from their instances. The only ones with the power to ban you completely are the lemmy.zip admins.

There are some power tripping happening here as well, but you're a lot less vulnerable. Just don't be a jerk and you should be alright. :)

Karma points is not really meaningful here, so I'm not sure if there's a way to view it from Lemmy.