Nothing weird about it. The HN guidelines[1] make it clear, IMO, that while some self-promotion is fine, the intent here is NOT to use the site primarily (or exclusively) for self-promotion. The account that submitted the userplane.io link had only ever submitted two links, and both were to userplane.io. What do you expect to happen?
Please don't use HN primarily for promotion. It's ok to post your own stuff part of the time, but the primary use of the site should be for curiosity.
> After a few more experiences like that, I've mostly stopped posting because it doesn't feel like the effort is worth it
Ironically this is exactly the wrong response. You should post more, but more stuff that's simply intellectually interesting, and not just to promote your own stuff. But if your only reason for being here is self-promotion, then you're right... not worth it. shrug