If it is for violating Imgflip ToS, you can do a ban on your own, but you should let an owner like myself, kewlew, or Gryphonstar know why you issued a ban so that we know what's going on. As for stream rules violations or unbanning people, I think it makes more sense to ask a stream owner. The bans feature is still pretty new and the stream owners are still working out how we should navigate this feature.