A somewhat different issue: is it possible to delete my own account? Not that I'm contemplating such a drastic step, it just seems that if a person had decided to leave the Monastery, it would be polite to delete or at least de-activate his/her account.

If you want to "de-activate" your account, you can do it yourself. Just change your email address to nobody@example.com, then change your password to LONG random garbage so you won't remember it. Also make sure you kill browser cookies etc. AFAIK this has been done before here.

Best throw your HDD (or whole computer) out of the window, destroy backups, burn your fingertips, pour acid on your face, pull your teeth, set fire on the house and run like hell!