I have reproduced the issue with gnome-system-tools in jaunty, 2.22.2-0ubuntu3, and have verified that the version in jaunty-proposed, 2.22.2-0ubuntu4, does not allow the creation of a user id that matches an id that exists solely in the group database (pulse-access is another example of this). Other user and group management continues to work.
There is still an issue that is likely difficult to solve, due it being the result of packaging policy; admins are not prevented from creating a user that later is created by a package (e,g, create a nut user/group, then install the nut package).
I have reproduced the issue with gnome-system-tools in jaunty, 2.22.2-0ubuntu3, and have verified that the version in jaunty-proposed, 2.22.2-0ubuntu4, does not allow the creation of a user id that matches an id that exists solely in the group database (pulse-access is another example of this). Other user and group management continues to work.
There is still an issue that is likely difficult to solve, due it being the result of packaging policy; admins are not prevented from creating a user that later is created by a package (e,g, create a nut user/group, then install the nut package).