Many forums don't offer an unread marker because of the database overhead to keep track of last seen message of each topic.

But there are ways around that mid even been better, because it is always a pain if there aren't nice ways to remove the marker which is often the case (like visiting each unread topic).

One light weight version of the "unread message feature" came to my mind 2 days ago in discussion with Brad Rushworth (see https://www.hostedredmine.com/boards/1/topics/105).
In short, why not simply mark each topic which have a new message since last visit. That way everyone with is logged in see the new messages and read only the one of interest. After the next login the uninteresting messages are mostly also unmarked (only one which new messages since then not). An unmarkall would then also nice feature.

It would also be possible with a small db overhead to only mark new messages of a specific forum or maybe add something like generic filter (date, keywords, forums etc.) in mark or remove mode (or maybe more) to the forum. So everyone could have a custom selection/mark pattern for the forum.

That are just some ideas, but it would be great to have a user friendly forum, because it is really limited at the moment, compared to the rest of redmine ;)

Whatever, would be nice to let me now what you think about it.