Let's use Mike's latest response in the identities bug report as an example. He posted saying it was fixed, and I viewed it before he moved it to Resolved Bug Reports and the thread was consequently marked as read. Mike then moved the thread from XenForo Bug Reports to Resolved Bug Reports, which had zero new posts. When I went back to the forum list, the Resolved Bug Reports forum was in bold as if there were new posts, but there weren't. Going into the forum proved that, which consequently resolved the issue; additionally, if I were to go on the New Posts page, the thread wouldn't even appear there, rightly so, because there are no unread posts in that specific thread.
It should be noted, though, that the person moving the threads doesn't notice this because they are taken back to the threads after they're moved.
Hope I explained myself well.