I thought, well my account is new, but I've seen 2hrs old account submit "Show HNs" with urls, easily.
And you get penalized for not posting URLs.
''On HN, the idea is for people to submit stories that they ran across and personally found intellectually interesting, not because they have something to promote. It's fine to post your own work, as long as it's interspersed with interesting posts from unrelated sources. But when an account submits promotionally, it feels like they're not participating as a community member, and HN users notice this and flag the posts.
It's best to build up a track record of interesting submissions from unrelated sources, and to intersperse your own articles with those. The software considers submission histories adaptively, so if you do that, your own-posts will eventually stop getting filtered.
If you dig up interesting things from a variety of places, things people haven't run into before, then you'll be perceived as a community contributor rather than someone trying to market something. Particularly good are stories on out-of-the-way topics that rarely or never get attention. The best submissions are the ones that can't be predicted from any existing sequence.
(Note: avoid posting major sites like youtube, twitter, medium, etc., for this purpose, because the software classifies them alongside the promotional posts so they won't help 'dig you out'. Ditto for Show HNs and Ask HNs (text posts) - avoid those until you're in the clear.)''