CriticMarkup was unveiled a little bit ago, and it was intriguing but not immediately useful to me at the time. Since then I’ve been playing with the MultiMarkdown Composer beta (available to owners of version 2), which includes a basic “change tracking” feature supporting full CriticMarkup syntax as you type. I’m sold.
This is a companion discussion topic for the original entry at https://brettterpstra.com/2013/05/18/criticmarkup-in-marked-1-dot-4