On some of my forums (which are still running phpBB) we have a section called the "Black Hole" which is where we put threads that we don't want in the limelight, so to speak. Threads with more sexual content, etc. They're still available to the public, however we've set it up so that:
The section does not show up in any search
The thread titles are not shown on the index (it shows "no posts")
Anyone have an idea how to do this (or want to create a mod to do it) in SMF?