I agree that merely posting on HN doesn't constitute a public launch. But what about meeting all three of the conditions I laid out in the sentence you quoted:

I agree that merely posting on HN doesn't constitute a public launch. But what about meeting all three of the conditions I laid out in the sentence you quoted: (1) marketing the site to the public, (2) accepting users, and (3) taking payments. Arguably, at that point, you have veered out of hobby project territory and have publicly launched a business -- and that's where my criticism lies.