I am not doing anything special or customized - when I click on the "Add User" button in the Admin site, the resulting page has two fieldsets:
the top is for adding username, password, password confirm and there are text fields like I'd expect
the bottom half shows another block like the top, but without text fields, along with a message about "First, enter a username and password. Then, you'll be able to edit more user options."
looking at the templates, the admin/auth/user/add_form.html overrides the admin/change_form.html and adds content for block after_fields_sets - and this block uses template variable 'form'. Since form is not defined, there are no text fields generated
admin/change_form.html is the template handling the top block, which uses variable adminform. Thus the input text fields get generated. On submittal of this form, a new form gets shown, one with all the user related fields. So functionality isn't impaired
My inclination is to guess that auth/user/add_form.html hasn't been updated to deal with some new logic, given it's 3 years old. Or is there somewhere else where adminform never gets set, and instead template variable 'form' gets set?
right now, having two formsets that show the same set of fields, and one doesn't have text fields, makes things look quite broken