Comment 7 for bug 47861

Incidentally, Jesús, that *is* checked. The code contains:

                        if ! LC_ALL=C expr "$USER" : '[a-z][-a-z0-9]*$' >/dev/null; then

(expr implicitly prepends a ^ to the regex) and in my tests I got an error properly displayed when trying to select a username containing spaces or symbols. So, if you file a bug about this, I'll need specifics.