[@netweb Keymaster 13 years, 6 months ago]

Currently this is not possible but it is a great idea that maybe one of the “bbPress Unread Posts’ plugins could add this functionality.

https://wordpress.org/extend/plugins/bbpress-unread-posts/
https://wordpress.org/extend/plugins/bbpress-mark-as-read/
https://wordpress.org/extend/plugins/bbpress-pencil-unread/

Note: Apologies, your post had been marked as spam for the past month :/