here also the same.
Today In my communication Tab i got 2 updates. i just a read two of the thread. then after i go to the home section. again the communication showing 2 that is old readed message as un readed.
one of the thread people suggested me to avoid some sort of behavior falls from sometimes browser cache problem.
anyhow i cleared the catche and re-login again. same behavior.
here i attached the snapshots.
http://imageshack.com/a/img4/253/pajl.png // i readed already it is showing again in communication tab. and also another problem you can see the rectangle box i gave to the thread it is not showing in the preview.
please see this pics i gave a reply.