> Please don't use HN primarily for promotion.
If your first and only post is to promote something on HN, then you are by-definition using it primarily for self-promotion. You need a tenured account to guarantee that your post isn't autoflagged and removed.
Even comercial post are fine if they are interesting.
The problem is when it's too off-topic, or too much empty marketing without information, or too much hype or ... there are a lot of reasons that can cause a post to be not interesting.
I don't know how the server decides which post to kill. I've seen some false positives and some flase negatives, vouched a few and flaged a few.
It is different when someone submits their own site again and again and again. (Unless it's very interesting, but if someone repost their own site too many tiems 99.9999999999% of the time it's not interesting.)