Uh… Sounds like it’s not really system’s fault, your setup is just terrible.

I don't know his specific issue, but the general behavior of systemd going completely nuts when something is a bit 'off' in some fashion that is supremely confusing. Sure, there's a 'mistake', but good luck figuring out what that mistake is. It's just systemd code tends to be awfully picky in obscure ways.

Then when someone comes along with a change to tolerate or at least provide a more informative error when some "mistake" has been made is frequently met with "no, there's no sane world where a user should be in that position, so we aren't going to help them out of that" or "that application does not comply with standard X", where X is some standard the application developer would have no reason to know exists, and is just something the systemd guys latched onto.

See the magical privilege escalation where a user beginning with a number got auto-privileges, and Pottering fought fixing it because "usernames should never begin with a number anyway".