Only works on the Forum home page, unfortunately. The portal page is a separate add-on, and doesn't support some of these little tchotchkes.
Rojo - definitely use the
Unread Posts link instead of just looking at the last 10 threads on the Portal page. You can choose to view just as many or just as few posts as you like, but as you visit threads, it then only shows ones that have been updated since you visited them.