User blog comment:Dopp/Message Wall Now Available in Labs/@comment-1318845-20120127005701/@comment-1656630-20120127174533

Sort of. The notifications clear when you visit the thread page itself (by clicking on the message title), respond, or click "Mark all as read" in your notification dropdown. But it should also clear much more easily if you're coming from that notification bubble. We'll have it fixed soon.