I can create an account with literally an empty password, but after logging out of the newly created account, I can never get back in because you can't log in with an empty field. Is this intended? Not that it really matters for me since I only go anon. The only side-effect is that there is a trail of abandoned throwaways behind me.
while it is possible for you to use the single letter 'a' as your password, i'd recommend against it :)