A reference implementation isn't standardization. Markdown had a reference implementation and yet subsequent implementations still diverged. The reference imple

A reference implementation isn't standardization. Markdown had a reference implementation and yet subsequent implementations still diverged. The reference implementation also had bugs, which were fixed over time, thus changing the de-facto standard. At this point, Markdown does have a real standard, CommonMark. GitHub-Flavored Markdown was modified to become an extension to CommonMark (it's literally just a few extra features on top of CommonMark at this point). There are of course non-CommonMark-based implementations still (such as MultiMarkdown) but at this point anyone adding Markdown support to a project should be using CommonMark or GFM.