Please don’t say HN uses any form of Markdown. It’s its own thing entirely with absolutely no foundation in Markdown—the only points of
any similarity between Markdown and HN comment formatting predate both by multiple decades. HN’s formatting gives you paragraph breaks (by blank lines), linkification (with no delimiter,
unlike stock Markdown which requires angle brackets, to the surprise of many), monospaced blocks (by two space indentation), italics (with asterisk delimiter), backslash escaping for asterisks, and that’s
all. Every element of this, or a very slight variant, has been common in lightweight markdown languages since before Markdown, and all but the backslash escaping and hyperlinks (which hadn’t been invented yet!) have been in conventional use in communication since well before the web (and match some typewriter conventions from before the invention of
computers).
Markdown is not the only game in town. Yes, for now it’s the dominant lightweight markup language (more’s the pity—it’s a right mess, thoroughly unsound and inconsistent in a great many ways), but a lot of stuff exists beyond its horizons; it’s only an instance of LMLs, not the whole class.