this page should probably be linked to on https://news.ycombinator.com/newsguidelines.html, I had no idea there were specific rules for the 'Shown HN' prefix
Btw, it's been on our list for a good 7 years to ask people to confirm that they've read the rules before posting a Show HN, but I always hold back because it would break a certain precedent. HN doesn't tend to use nag screens and so on.