I think the individual post links are deteriorating. For example, when looking at a thread under the communications tab, it might say "in response to BluShadow" with BluShadow being a link to BluShadow's profile. When looking at a thread under the Discussions, the link points to what apparently was intended to be the post being replied to (and I think it used to), but now points to the beginning of the thread. Looking at the link, it appears to have the thread number followed by #, followed by the thread number again. I think that latter is supposed to be a post number. Perhaps fixing that would fix bookmarks.
Software improvement is supposed to fight entropy.