It would be best if this button was shown to everyone who has the ability to add or remove specific user rights, because on some wikis it's not just admins and bureaucrats who can do this.

@MarcoAurelio As far as I know, we have no formal policy on the adding of user rights. However, considering the fact that no one objected to the proposal and there were a considerable number of !votes in favour of adding the permission to the group, I think it's fairly safe to assume that an RFC or something similar would end up with the same result.