One thing I have used alot in phpBB3 is the "View your posts" button.
It lists all the threads I have ever participated in, show bolded titles for ones that have new posts.
It's very handy. People use it (http://www.avforums.com/threads/participated-threads.1825342/ )
The almost equivalent in Xenforo is "Watched threads".
Does Xenforo have a participated threads (vB) or "Your posts" (phpBB3) addon ?