The concept on which the WixForum is currently structured, is that the WixForum administrator is also required to be the Manager or the Owner of the website it is being built on.
Why? Because, the Forum Administrator can not create a new category or change the name of the category, or change the visual design of the category, or change the credentials of the category, or work on the spam and filter options etc, if he does not have any permission for the site mangement and site editing.
If those features could be managed thru a password protected user interface, without letting the Forum Administrator to dive into an area where he should not be touching (like places where domain settings and/or site configuration are managed etc), it would be perfect.
Otherwise, the current structure is hindering all of us to offer a self-service option to our clients. Please imagine a situation, where the Site Manager and Forum Administrators are different people, and they are very far away in both distance and timewise. Can you imagine the problem of maintaining the Site and the Forum?