All that said, I don't think it'd be bad for the mods to have a private way to communicate what they did, though a repository is too much. Maybe somewhere for a mod to say, "hey guys, I don't know what to do..." and another to respond. It'll build up like the forum already has.
SMF thought so too so its built into the moderation system with all reported posts, and if a moderator is questioning and wants to ask other moderators he/she can just report it with their comment for the other moderators to talk about.