This works great, one can hide threads and forums perfectly, which are then not shown in the newsfeed, thread list and forums list. Also, the threads are not displayed on the forums start page and, for example, not in Siropu's "Recent Posts" addon. It works cleanly and fully integrated.
With this addon, my visitors can hide individual threads or entire sections in the forum that they simply aren't interested in - a long-held wish by them.
It would be very useful if the addon could additionally be used to hide albums (and not only categories) in the official Xen Gallery.