[nerdponx]

From what I remember, John McFarlane and his Pandoc project helped a lot in getting CommonMark adopted.

Github used to have its own "Github-flavored Markdown" before CommonMark came along.

[mikl]

Correct, he (jgm on GitHub) is still by far the biggest contributor to the spec: https://github.com/commonmark/commonmark-spec/graphs/contrib...