I think that’s a perfectly fair argument, and I think you’ve been somewhat unfairly treated here on Meta.
Many developers don’t do any advertisement for their work, and eventually give up on their projects because they couldn’t garner any interest. I can’t fault you for trying to get your name out there.
That being said though, keep these things in mind:
Unwritten rules are still rules. Just because Meta isn’t officially or explicitly stating (or maybe it is, but it’s hard to find) that commercial advertising isn’t allowed except within Category X and Y, you should still take great care to listen carefully when told to show off your wares elsewhere. You went with the “ask for forgiveness, not permission” approach, which is fine, but now it’s time for the forgiveness part.
Contributing back to Discourse can be a great selling point. As a frequent customer of premium WordPress products, I can attest that I’ve always preferred sellers who’ve had some involvement with the WordPress open source project, either through a popular open source plugin or direct contributions to core (WooThemes did both, and they’ve now been bought up by Automattic/WordPress.com)
You don’t wanna get off on the wrong foot with the community that you’re trying to enrich.