Due to an influx of spam, we have had to temporarily disable account registrations. Please write an email to accountsupport@archlinux.org, with your desired username, if you want to get access. Sorry for the inconvenience.
https://gitlab.archlinux.org/archlinux/mkinitcpio/mkinitcpio/-/blob/057586f9195e81fd70ea06cb35a4c05acedff864/mkinitcpio#L566