A post that fits the published rules, so the outcome is luck rather than a removal.
The Show HN rules are published, so this is one of the few launch channels where you can be certain what is allowed. Most removals are people who did not read them.
Show HN is for something people can try. Not a landing page, a sign-up page, a newsletter, a blog post or a list. It must be non-trivial and made by you.
It should be easy to try without a signup or an email gate. This is the single most common reason a Show HN gets no traction.
Show HN: followed by a plain description of what it is. No adjectives, no exclamation marks, no pitch.
What you built, what it runs on, what was hard, and the specific feedback you want. Then stay in the thread and answer everything.