Just so we're clear -- if a topic was seen when it has new posts in it, hitting 'mark unread' will immediately mark THESE posts as unread. While if I for instance just visit the penultimate page of a read topic and hit Unread, it'll mark the entire topic as unread, instead of simply the last two pages. Which would make more sense... To me, 'mark unread' should basically say, 'come back here when I want to see this topic again'... Like a bookmark. At least that's how I use it...