Some wikis have more different rules than others when it comes to a possibly-growing administration team, so nobody truly knows at the least if they need more administrators at the moment.
A good place for the admins to start is by actually making an easily accessible Wiki Rules page. Unless they do that, anyone can claim blocks and / or promotions are either unfair (In the case of blocks) or unwarranted (In the case of promotions) as a Rules page should detail how users can become promoted to local moderation roles.
