Not sure if this is 'as designed' or not, but I've created a user upgrade which when applied allows them to set their own user title.
This works fine, but if I downgrade them the user title stays as they set it. The only way I can see to revert this to the default titles, is to manually edit their account details. They can't do it, as the option to change it is obviously removed when downgraded.
The other upgrade of adding a group ribbon applies/removes as expected.