Beyond Markdown

An essay by John MacFarlane, the father of Pandoc:

In developing Commonmark, we have tried, as far as possible, to remain faithful to John Gruber’s original Markdown syntax description. We have diverged from it only occasionally, in the interest of removing ambiguity and increasing uniformity, and with the addition of a few syntax elements that are now virtuously ubiquitous (like fenced code blocks and shortcut reference links).

Source.