Invisible messages

[Telemacus]

I don't know if this can be done yet, but I think it would be quite useful.
I wish I could have a feature which allowed some forums to let users post messages but only the user + moderators and admins where able to see it.
I know I can create a group where all messages posted by users in that group automatically become invisible until they're accepted by the moderators, but that's not what I'm talking about, I want the user who has written it to be able to read them as well.
For example, I have a forum called "complaints" and because this is a touchy subject, I don't want other users to be able to read what others complaint about. However, sometimes a user is right about his complaint, and I would like his messages to be visible to moderators so that they can act.
This way the users would get to see the answers to his complaints while keeping this a private affair.
Of course, the user could post a message to the moderator, but if there's a team of moderators, then the first one to read it can act accordingly. (not to mention that the answers to those problems can be used for training future moderators).