Markdown having *italics* _italics_ **bold** __bold__ instead of _italics_ *bold* was such a mistake.

No idea how non-technical people were ever supposed to grasp that.

So does John McFarlane, the author of djot (and perhaps more widely known, Pandoc):

<https://github.com/jgm/djot>

My own convention when writing Markdown is to use single underbar for _italic_ and doubled star for **bold**. Except of course on GlitchSoc (a Mastodon server), where underbars give underscores, and single or doubled stars are for italic / bold respectively.

But otherwise, if I see a singleton star or doubled underbar in my own writing, I'm pretty sure I've typoed something.