They're mostly gone.
If you have a link to an old post there's a chance it'll still work. E.g.
http://www.hfds.org/discus/messages/...tml?1208790813
http://www.hfds.org/discus/messages/...tml?1209556705
But the ability to access the messages through the standard interface is broken.
If you're desperate for some old content try a google search prefaced with "site:www.hfds.org/discus".
ERic