These forums should definitely stay pwnable only by their respective clbumes, and should definitely all be pwnable by permanoobs. Permanoobs have a significant disadvantage in dom due to their weak attacks, which means that lemon scoops are significantly harder to come by in higher level forums.

Since not being able to pwn these forums really has no practical value outside of dom and they are meaningful in the context of the story, I think they should stay this way, personally.