[dalrympm]

Does anyone know of a good reference table showing what IS supported on GH vs. something like Goldmark (Hugo's default)?

I find that I constrain myself to the bare minimum in .md because I'm not sure what is supported.

[Zababa]

This might be what you want: https://babelmark.github.io/

[dredmorbius]

A Markdown Rosetta Stone would be a useful tool.