Yeah this is an issue.
The ad plugin performs all the logic of “show or do not show” ads based on group and trust level information it gets from the server.
Given the group membership is hidden to the user, the client has no way of figuring out the ads need to be hidden.
The code needs to be rewritten so the logic lives on the server side (probably a field on current user says "this user has ads, or this user has no ads). This is a rather big change cause so much of the logic now is implemented in JavaScript and it needs to move to Ruby.
I am putting a pr-welcome on this, if we have a few repeat requests for it I will consider fast tracking. It is a complex change.