Safari on macOS will not load this address. It does resolve, weirdly, "host" in the Terminal works and I can see Safari's requests being answered by my home DNS server in the logs.
But Safari just throws an error: Can't connect to the server "ai".
Update: It works if you include a trailing dot: http://ai.
Update 2: HN's URL parser does not include the dot in the hyperlink. Frustrating.