At the very least, DH does not store passwords as plaintext, but it's only very marginally better than that. Passwords are stored using a custom-rolled symmetric encryption algorithm created by... I never found out if it was a founder or just one of the earlier admins, but that doesn't really change much. For what it's worth, I never ran across the key to this, which is at least somewhat good in terms of security, but it's quite possible that this is true only because I never actually went searching for it, especially given that all of the devs and dev interns have root on most of the systems.