This question was asked before, but the answer was just to use Mail 6.x with Mountain Lion -- and that's not working for me.
The question is:
I have a Mail.app rule that copies certain incoming messages into an archive mailbox. I'd like those messages to be marked as read in the archive mailbox but remain unread in my in-box until I actually read them. I tried adding "Mark as Read" to the copy rule but that marks the message as read in both the >archive mailbox and my in-box, so I never have any unread messages in my in-box.