From the Show HN rules: <a href="https://news.ycombinator.com/showhn.html" rel="nofollow">https://news.ycombinator.com/showhn.html</a><p>> <i>What to Submit</i><p>> <i>Show HN is for something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread.</i><p>Unless you are the owner or made a significant part of the linked site, it's not a good candidate for a Show HN.
I often mention this in discussions of regular expressions to validate domain names. (As far as I know, it's the only DNS A or MX record that contains only a single label.)