Explains how it wasn't necessarily his first thought. In the beginning, it was HN comments where the first thought is more sharing content you feel is relevant, or the gamification of karma.
I'm responding to you and at no point do I feel like I am marketing "prawn" or anything I do online. I'd use a relevant username for one thing!
I have had profitable side projects but I never talk about them on HN or other sites.
Self promotion is inherently about marketing and even at the start that is precisely what he did.