It seems that "Unread Posts" doesn't work consistently. Sometimes show none, sometime some new posts, however it seems never full list.
After clicking on "Mark all messages as read" from main page, wait a while and refresh the page in order to spot indication in some section usually watched that new message is shown, then click on "Unread Posts" link. It will usually not be shown, although, sometimes, after some time passed it will show some, however not all new post list. All under the same log session.
If you click "mark all as read" then it will assume that all sections were read and take it from there.
It will also only show posts you were involved with in some way.
Be that watched or took part in.
IIRC it does not count your post as a new one as it assumes you know what you wrote.
The forum software is not the best in the world and does have some shortcomings but works for what it does.
The same can be said for email alerts which can on occasion come AFTER you have read a topic you were involved with (better late than never approach).
