Edit from MoodleHQ chat...

Petr ?koda:
1 - there is some problem with "manual only" - it should be IMO just manual now and should be enabled all the time.

2 - You can login even when your auth is disabled - or at least it tries to login and throws errors

3 - the login page does not display the right pane with instructions properly - there is some logic problem

 ... one more auth idea, maybe we could add some 'suspended auth type' and admins could disable accounts by changing user auth to this plugin which would not allow login and throw custom warning, but would allow loginas. ??

Martín Langhoff: makes sense. we'll have to fixup like auth/ldap and auth/db to not try to create a duplicate user acct in that case (in the sync scripts, that I want to fold into cron properly).

Petr ?koda: IMHO they should expect that the username might be taken by other auth plugin anyway

Martín Langhoff: yep - have to check what the applicable cases are there.