(Actually, to be more specific, a YAML file with no directives, explicitly-signalled start-of-document-content, and followed by a second null document. I will note that frontmatter syntax is not specified; the non-normative Appendix B is the only place that suggests it means prefix and suffix --- lines. And no, frontmatter is not part of Markdown, or CommonMark, and is in fact incompatible with both. And it’s invalid YAML too, the end-of-frontmatter line should be ... to indicate end of document without starting a new document.)
Looks like unless something better comes up, we'll be stuck with it for a while.
I find markdown useful for repo-specific conventions, especially skills.
"Ensure stakeholders are aligned on what matters most and why"
But it is instructions for LLMs, right? A way to describe something that the humans know and the LLMs don't.
LLMs literally cannot be stakeholders, by definition.
For example, readability. Where are the developers out there saying "I am very willing to sacrifice a lot of readability to get even a small improvement on e.g. abstraction cleanliness", and sticking with it?
Or "performance can take a huge hit at the cost of being dead easy to read and reason about". Coming up with a list of abstractly good-sounding qualities is just prosocial signaling without knowing what you're willing to sacrifice. There should be a FUCKIT.md that enumerates these.