What is the (deeper) issue? This is a reasonable question with a reasonable response with a couple of trolls below.
It isn’t much use to link to every systemd issue under the sun that is debatable.
The point that the linux kernel does not accept DNS compliant hostnames either is fair. There’s a lot to complain about in systemd but this seems like a relatively minor nuisance.
Maybe we should add a flag for “people-who-hate-systemd-far-more-than-is-healthy”.