CommonMark
A Valiant Attempt to Standardize Markdown
CommonMark is the result of a collaboration lead by JGM (the creator of Pandoc) to create some sort of agreement between all the different companies and organizations using Markdown and splintering into dozens of different flavors all interpreting the non-standardized original in their own way. The effort was a success overall, but left out several design decisions including tables. That’s right, CommonMark does not allow the use of any tables. Tables were one of the main additions from GitHub that people wanted (despite the pathetic design of GFM tables that often requires a tool of its own just to make them). Given how bad GFM tables are, it is no surprise that JGM politely left them out and quietly implemented a far superior — and simpler — design in Pandoc Markdown, which is one reason why the resulting Pandoc Markdown is by far the simplest, cleanest, and most widely applicable Markdown version today. It has clearly demonstrated its design supremacy with its adoption into the R language and more (even if GitHub and the rest never catch up).