This is the core error of understanding, and that same error leads to a great deal of bad Show HN’s as well:
Platforms want repeat business. Or, in classical retail cafe terms: Platforms want regulars.
Signing up for Reddit solely to self-promote something is indistinguishable from how one defines ‘spam’: unwanted promotional links delivered from reputation-free accounts. HN chooses to tolerate the Show HN flood to some degree because it’s classically of interest and open by design, but also comes with a dramatically more expensive human moderation burden that Reddit has decided they would rather not pay.
That I can summarize this post as “Self-promotion by unreputable or disingenuous participants is usually a bannable offense in online communities”, without having to even name whether it’s Reddit or HN or MeFi or RPG.net, suggests that this is much more a ‘fuck around and find out’ learning moment for the author than something of material interest to HN. Certainly there’s no surprise at the outcome: a competent anti-spam automation that triggered the first ban would have banned the domain regardless of which account is involved, to prevent swarm bot attacks that are well-known for some years now to webforum operators.