One of the boards I used to be on had a section for each actor and each character and you were not allowed to say anything negative about the actor or the character while in those sections…and the mods heavily enforced it. In other sections you could say what you wanted but most people stayed pretty polite…some of the actors and writers actually frequented there.
Other forums I’ve been on used to sticky character and actor appreciation threads at the top so they wouldn’t get lost in all the new threads.