The old search function is gonegonegone, it was putting too much stress on the servers. The DIS now has an off-site system called BoardTracker. The ONLY way I know of to keep track of interesting posts now is to subscribe. To every one. To each and EVERY one you like or post on. The "new" way to look for "See all posts by this user" doesn't seem to work anymore, I don't know why.
I haven't been over there lately, but "BoardTracker" used to post on the Technical Support Board, not sure how active he is these days.
The Webmasters seems to be aware of the various issues folks have with the BT system & fixes are apparently in the works (but I am not aware of any particular timetables for this).
If you have a specific problem, post on the Technical Support forum - maybe they can help you.
Good luck - if all else fails, you can post that you're looking for a particullar thread, Maybe another DIS'er is subscribed to it and can post a link.
agnes!