PMs aren't encrypted.
Forum database includes PMs, deleted PMs, is encrypted and only admins, global moderators have access to database.
Bitcointalk.org Privacy concern questionDeleted posts are almost never removed from the database. A PM is removed from the database if the sender and all recipients delete it.
Full database backups are created daily, and all global moderators and admins can download the (encrypted) backups and implement their own rotation policies.
they can download the backup to have it at multiple locations, but it's useless for them because they don't have the decryption key
This.
Only me, Gavin, Satoshi, and Sirius can decrypt it.