Ubuntu username fail

So Ubuntu is pretty easy to use most of the time. But I've installed the system probably about two dozen times now, and each time I forget that I cannot add a username with a dot without doing some somersaults.

You cannot use the Gnome users-admin control panel to add a username such as "nels.nelson". Oh no. That would be horrible.

Instead, you have to use adduser.

sudo adduser nels.nelson --force-badname
Password:
Adding user `nels.nelson’…
Adding new group `nels.nelson’ (1002).
Adding new user `nels.nelson’ (1002) with group `nels.nelson’.
Creating home directory `/home/nels.nelson’.
Copying files from `/etc/skel’
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for nels.nelson
Enter the new value, or press ENTER for the default
Full Name []: nels.nelson
Room Number []: 
Work Phone []: 
Home Phone []: 
Other []: 
Is the information correct? [y/N] y