The value of +*autoname is incremented when the page to add a card of that type is generated, whether or not the card is ever actually created. If they ever are not created, there will be gaps in the series of names.
"Another way to give someone an account is on the Options tab of almost any card, where you can click on "Add a sign-in account for |card name|". Enter the email address of the person you'd like to give an account associated with that card, and they'll receive an invitation email. People who have permission to make Invitations (as described above) can add accounts to existing cards."
How has this changed with the new permissions settings?
The link to add an account was gone at first (unintentionally), but should be back now for any card controlled by an *accountable setting that is "yes". Not clear what this has to do with autonaming though?