It also sees very wide use, it's not just a proof of concept - most who've used any recent major version of Storybook (84k stars) would know about it: https://storybook.js.org/docs/writing-docs/mdx

Not just Storybook, but most modern JavaScript-based static site generators, for example:

- Astro: https://docs.astro.build/en/guides/integrations-guide/mdx/

- Docusaurus: https://docusaurus.io/docs/markdown-features/react

- Eleventy: https://www.11ty.dev/docs/languages/mdx/

- NextJS: https://nextjs.org/docs/pages/building-your-application/conf...

Also Multidimensional expressions, popular in OLAP cubes. https://en.wikipedia.org/wiki/MultiDimensional_eXpressions

I came to make the same comment, so glad it's been brought up and reenforced.

https://mdxjs.com/

Came here to say this, confusion ensued.

marko or godown would be fun

Marko too is taken https://markojs.com/