I am sorry I mis-read your post
I agree I would like to see this to. A forum I visit has a 'fliter' button under everyones avatar in threads, if you click it the page re-loads and shows all posts by that user in the thread. These guys also hacked in 'display my threads' for forumdisplay and display my posts for showthread. There are a lot of large threads on that forum and I use these fetures multiple times everyday.