[Seirdy]

Goldmark (Hugo) and many Markdown extensions do support description lists. Hugo also supports render hooks which make adding support for attributes, picture elements, etc trivial. And the vast majority of advanced markdown engines support a front matter, typically YAML although Hugo supports TOML and JSON as well.

[toastal]

So you have to pick your lock-in for a Markdown processor? Once you step outside of CommonMark, nothing is compatible. Compare that to AsciiDoc, reStructuredText, Org mode… these support metadata as a first-class feature (as you would expect from almost every other creative format: *.ogg, *.webm, *.odf, *.png, *.svg, *.html, etc.). Choosing such tools makes it a) harder to migrate to another tool & b) difficult/impossible for other tools to render it properly. You can skip that nonsense by just choosing a better format.

[Seirdy]

It's a very common Markdown extension supported by PHP-Markdown-Extra, Goldmark, Pandoc, Kramdown, and dozens of others. Several of these have supported it for almost ten years now, with the same syntax.

PHP-Markdown-Extra is the closest thing to a standard with more than GitHub-Flavored-Markdown; several other Markdown engines use its featureset as a baseline for compatibility for anything not present in GFM, even blocking the shipping of new features until after PME agrees on a syntax. So you can think of CommonMark as the lowest common denominator, GFM for an intermediate version, and PHP-Markdown-Extra as something suitable for building more advanced websites.