Global accounts currently cannot be blocked, so that stewards must lock users out of their accounts to stop them. This is very user-unfriendly, as it does not give an error message. From the user's perspective, their session simply disappears and their password no longer works. This makes account locks impossible to appeal or even understand for the vast majority of users, which exacerbates the situation of false-positive or legitimate users.
It would be very beneficial to allow stewards to block accounts, with an appropriate you've-been-blocked message when they try to edit or create/unify local accounts.