There’s simply no “HN is not for self promotion” policy. You’re asked to not use your account primarily for self-promotion, and repeats are allowed, so you can roll your dice multiple times on your Show HN already as long as you’re otherwise a good contributor to the community and only do it sparingly. Flooding another topic with commercial promos simply turns it into another https://news.ycombinator.com/show, what’s the point then?

As for YC companies getting Launch placements, well too bad, it’s their site, you’re free to leave and start your competing one. I assume most users aren’t bothered — I seldom notice them and hardly ever click on them. I notice job ads more.