Favorite Random Markup Language

Recently, I've been pretty interested in markup languages for hyper-specific tasks. Things like, CookLang[0], Traindown[1], and Fountain[2].

I was wondering what other kinds of similar projects people have seen?

[0]: https://cooklang.org (for recipes)

[1]: https://traindown.com (for workout logging)

[2]: https://fountain.io (for screenwriting)