Here's a fun trick: if you add .text to any URL on Markdown creator John Gruber's blog you'll get to see the hand-authored (bar the metadata and tags bits) Markdown he wrote for that entry.

Example: https://daringfireball.net/linked/2026/01/09/moylan.text

... and if you look closely at some of the entries you might spot custom Markdown features that aren't part of the published spec.