Update:
Jetpack now has its own built-in Markdown block:
I’d highly recommend using it instead 🙂
Original post below:
I’ve been playing around with Gutenberg a tiny bit recently and have realized that, at least in my case, it kind of eats the Jetpack Markdown module and doesn’t offer full markdown support.
I honestly know nothing about writing blocks for Gutenberg, but luckily GitHub user nuzzio does 🙂
This recent, but now closed PR to Jetpack was pretty much everything necessary to build a working block.
I’ve put my code up on GitHub as a WordPress plugin:
Like I said, I don’t know what I’m doing–so consider this plugin super beta.