Kolektywne konto administracyjne.
We’re working on that, but not there yet.
Polskie tłumaczenie, z drobnymi zmianami: https://szmer.info/post/356383
We’ve just published a polish translation of this, with some minor changes; https://szmer.info/post/356383
It does not. Other then running a private/closed instance there’s really no way to limit input from anyone with an account.