as long as you're able to register it with a valid DNS record attached, anything can work as a domain, even an emoji.
ohhhh yeah anything works (i only thought it didnt because of the "don't add any subdomains" part in step 5, i already knew emojis worked because of punycode though)
i think they meant that you can't add subdomains of the domain you've configured, so i can't add additional records for "haha.sus.omg.lol" and expect it to work perfectly - however i've never tried that and i'm not going to either :)
also yes it's mobile unfriendly but i don't think the old site was very friendly either so
loving the new look keep on