Doesn't mean I want systemd silently escalating my process to root when I think I've told it to contain privileges of the process to a specific userid. Clearly

Doesn't mean I want systemd silently escalating my process to root when I think I've told it to contain privileges of the process to a specific userid. Clearly the correct behavior for such a program is to throw an error if it is rejecting a username for ANY reason, even when that reason is supported by stilted reasoning.