For example, I didn't read forum whole day, then in end of day, I have got message notification, and:
1) login
2) saw many new posts, but didn't read (was too late)
3) read new posts in topic with notification
4) logoff
5) went to sleep
NEW daY!
1) login
2) ?!?!?! no highlights, everything "readed".
May be I wan't read all stuff

Everything was fine until certain moment.
It's just feedback.