I use the heck out of Critic Markup, but I don’t have a lot of time to make all the tools I want. Some awesome people are taking matters into their own hands.
CriticMarkup.js converts the syntax into HTML.
Critic Markup support is now available in SmartDown, the Windows Markdown editor.
A Go library for Critic Markup
A version of the Go CLI for Critic Markup
FoldingText has supported Critic Markup for ages and it looks great.