I never understood why that rule doesn't include comments. Like if you posted a ton of helpful comments and zero posts, you wouldn't be allowed to post a link you made yourself.

I don't think there's anything wrong with promoting blog posts or apps you've made yourself unless it's really excessive. How are people supposed to get started otherwise? It's okay if you're a huge tech site, a big newspaper etc. because people will auto-post your new posts to try to earn some karma but who is going to do that when you've only got a handful of readers?