Hi Maintainer, I'm wondering if you have been able to further consider this possibility. I have made a patch for version 1.8.5-2 which strips spaces from the username, and it has been successfully deployed without issues at the Open Computing Facility.
The patch itself is only a few lines long, affecting the function "username_focus_out_cb". I would be happy to provide it if desired. As Andreas has previously noted, on Debian a username with a space cannot be created, barring manual editing of the username database. In particular, I have yet to see a single real example of a username starting with leading spaces, especially not one which would be used to log in to a graphical environment. Hence, there should be no realistic adverse impact by applying such a change. Best, Kevin