True, but if someone were to be banned in one community they can always join and make comments in another similar Lemmy community (or similar magazine on kbin). If they get banned on one instance, they cam join another instance. The Fediverse makes it easy to still contribute even if one avenue is closed.
As far as I can tell, there hasn't been any moderator overreach on Lemmy/kbin. Maybe everyone is starting off on their best behavior. Or mods are aware that the atomized nature of the Fediverse means they have only so much power or influence. Also, it could just be the communities/magazines I'm in but there haven't been a lot of heated arguments.
You can be banned here not only from a single “community” but also from entire instances, which the former would be comparable to a subreddit ban and the latter would be even worse.
In any case you can just spin up a new account on either.