I think you and I share some concern (horror?) about Markdown’s lack of spec and tests. The code is ugly to boot. Extending or customizing Markdown is tricky (we already have some hacks and they are terrible), and I worry about “bit rot” of content if the format doesn’t have a spec. I’m evaluating the possibility of starting over with a new implementation coupled with a real spec and test suite, and I’ve been thinking a lot about how to parse a language like Markdown in a principled way. I’m pretty fearless about parsers, by the way; I wrote a full ECMAScript parser in a week as a side project.
I want this new language – working name “Rockdown” – to be seen as Markdown with a spec, and therefore only deviate from Markdown’s behavior in unobtrusive ways. It should basically be a replacement that paves over the problems and ambiguities in Markdown. I’m trying to draw a line between what behavior is important to preserve and what behavior isn’t.