@technodad Thanks for the link and comparison. And for CriticMarkup.
@DandyLyons
Think of it like the markdown as a key feature set.
It is in all the other Markdown Flavors.
Github created extensions and the Multimarkdown was developed in parallel.
CriticMarkup is as far as I know a completely different extension.
Editors like Marked or Typora try to incorporate as many features as possible.
This makes the story even mor complex.
CommonMark tried or still tries to rectify that.
But they are still far from their goal.
(The reason why I switched to Asciidoctor and even thought me some ruby for it…)