As previously discussed it's allowed by POSIX and supported by major distributions and Unixen. The systemd team's assertion that it's not is based on a couple o

As previously discussed it's allowed by POSIX and supported by major distributions and Unixen. The systemd team's assertion that it's not is based on a couple of programs, mainly one Debian utility. Basically they don't believe that it should be allowed and they don't want to put in even the tiniest fix, so they're asserting that it's invalid based on prejudice.