I've tweaked my Emacs configuration default to github-flavoured markdown syntax for .md files. GFM is remarkably common these days.
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On the remarkably large feature set of format strings in common lisp, and comparing with an s-expression based syntax alternative: https://cs-www.cs.yale.edu/homes/dvm/format-stinks.html
It's funny how markdown has won in so many tools for prose, but doc comments syntax is so varied.
Rust and Julia are largely markdown, Python is ReST plus doctest syntax, and Java even an HTML dialect!