What I'd like to see is a moderation feature that actually prevents users from posting to a board unless their posting has been approved by the moderator.
I'm thinking of a published/unpublished status for each message which can be changed either by the admin or the moderator.

Grrrrr you mean it's not moderated? Here I was installing the SQL add-on modules

Here's how I think it should be organized, ideally. You would create the concept of "User Classes", and allow the administrator to assign the capabilities of each class. Guests get assigned "User Class 1", Registered users get assigned "User Class 2", and the admin would have to upgrade/downgrade users to other classes. Each "User Class" would be assigned a configurable set of capabilities. For example:

Guest
-----
Read (Y)
Post (N)
Approve (N)
Open/Close Threads (N)
Approve Messages (in moderated boards/threads/users, ie where posts require approval) (N)
Prune (N)
Delete their own messages (N)
Delete other people's messages (N)
Mark Users or Threads as moderated (ie the posts require approval) (N)

Other classes of users would be entitled Registered Users, Supervisors, Moderators, Administrators , and there would be a spare class for funky setups.

Regards,
Stephan