This is a good article, although I wish it had talked a little more about the standardization (or rather, the lack thereof) in Markdown. I get why it didn't, it's trying to be positive about something that is an overwhelming net positive for the world, but I think a "warts-and-all" treatment of the history would be more honest.
I appreciate that Gruber brought this very helpful thing into the world, but OTOH he was such a prick about the whole Standard Markdown debate, for no real reason other than ego. And it resulted in Markdown remaining an ill-defined standard to this day, with occasional compatibility issues still cropping up even though most platforms support most of "Github-flavored Markdown" (itself a stupid name and indicative how badly this has gone).
I _don't_ think it was just ego. I think it was a smart strategy because formal standardization tends to bring in complexity, and just letting folks go off on their own and document their own usage (or "flavors") ends up being Good Enough in actual practice. It sucks from a standpoint of what I personally find satisfying, to be clear. But based on what I've seen over the last 20+ years, it is the strategy that is much less likely to yield a format that gets captured by giant companies that own a hyper-corporate standardization process that eventually gets enshittified.
You've pretty much said what I was going to say. I think John was absolutely inspired in coming up with Markdown, but was a terrible steward. Or perhaps I should say he was unwilling to steward it.
My impression was he pretty much threw up a Perl implementation that was good enough for what he wanted, refused to refine it at all, and declared by the power vested in him by nobody in particular that if any parser implementation differed in behaviour to his (like, to fix bugs or make it better), wasn't true Markdown and wasn't allowed to be called Markdown.
Or perhaps I am being uncharitable in my interpretation of events.