The Junk forum is a non-viewable forum where all junked (deleted) posts and threads are sent to. Non-upgraded and L33t members cannot junk their own threads, however Ub3r, Mentor, Staff and Admins can. After a period of time, the Junk forum accumulates a large amount of junked posts and threads. Omniscient will empty the forum when it reaches this point and and reset the post count.
A user who has junked posts or threads can still see their post count without it being affected, but will be unable to view the Junk forum. If a user were to look through their recent post history, those posts would no longer show up for them.