What's wrong with self-promotion in comments? Is it against the rules or some code-of-conduct?
Imagine if everyone that had a blog, newsletter, rss reader, news aggregator site, or AI tool did this. What would that do for community and conversation? It would be miserable, we'd call it all spam.
Instead, I'd suggest making a root-level comment talking about the OP discussion and including their tool as part of their answer, as others have done. If they don't get visibility, so be it - that's how voting works.