I try to give a solution for our read/unread/new posting problem:
A posting is either
(A) a read
posting - following the cases Jens described - or
(B) an unread
An unread posting could either be
(B1) a new and unread
(B2) an old and unread
Therefore postings could have three different stati that ILIAS should handle:
The different ways of making a posting a read posting were already described by Jens. Are there any additional comments to that?
The difference between a new and an unread posting is the last visit of the user in the thread: postings after his/her last visit are new, others unread.
If we offer all the three possibilities for displaying the status of a posting we could help everyone, I guess. Those who are mainly interested in new postings see them directly. And if you enter a forum where already a lot of postings (all new at the first visit, later unread) exists, you can always distiguish between the new postings after your first visit and the postings that have been made before you subscribed to the forum and that you still want to read (if you do not want to read them, use the button "mark all as read"
Werner's idea of labeling postings is very good. But I would prefer to implement a solution like the one described above immediately to help those users like the PH Zurich team to handle their dozends of forums. And I think this way of implementation could be improved later with Werner's idea.