Board Thread:Support Requests - Community Management/@comment-4780692-20190703111032/@comment-1038387-20190703121354

Those rights can be altered by Bureaucrats; you're an Admin (what you call a Supervisor). Admins can only give people Chat and Discussion Moderator rights.

If there's no active bureaucrat, you can adopt the wiki. The rules for b-crat adoptions are the same as regular ones. If you succeed, you can then promote the other user to Admin (but don't promote them to b-crat).