Forum OpenACS Q&A: Search is broken
Mainly its cleanup of the code that is long overdue.
I am also looking into enabling the dynamic threaded forums user interface that was included in the Concord Consortium demonstration web site originally developed by Jeff Davis. This is a little tricky, since it was designed to work on OpenACS 5.2(HEAD).
Since it still supports flat forums, but greatly improved the threaded user interface, I think it is the best starting place for a user interface disucssion.