Note that the problem you describe is more a GDM bug. The gnome-system-tools don't handle the Login Screen at all. You should report a new bug about that.
Other than that, see bug 247910 about showing users with UIDs < 1000 in users-admin.
Note that the problem you describe is more a GDM bug. The gnome-system-tools don't handle the Login Screen at all. You should report a new bug about that.
Other than that, see bug 247910 about showing users with UIDs < 1000 in users-admin.