This is an Internationalized domain name (https://en.wikipedia.org/wiki/Internationalized_domain_name) - the actual domain shows up in browsers as マリウス.com but HN unfortunately doesn't decode or show it that way.

The author has a post on that, btw

https://xn--gckvb8fzb.com/never-click-on-a-link-that-looks-l...

I was befuddled too, thought it was an Elon Musk offspring's name or something. Turns out it is a Japanese character.