Depends on how it is setup.
All changes are kept in a diff like format so they can be undone if not acceptable.
So if someone comes along and changes/removes what Brian put in there, the owner of the Wiki can revert those changes back so the original content is still there.
I have not used it enough to know what other levels of access there are though. Ideally, it would use the same userid’s and passwords that the forum does, but I don’t know if such a bridge exists nor if Chris has time to play with something like that.