The CommonMark is definitely more readable, but Markdown is just so sparse by design that every time I tried to use it for anything more serious than e.g. a blog post I found myself banging my head against the wall, so it's a tradeoff I'm happy to make - and we're talking about languages whose purpose is to produce readable output, so while a readable source file is definitely a nice thing I think it's hard to make a case for valuing that over functionality. To title a paragraph in markdown you can choose from an <h[1-6]> or a <strong>, that's it, and it's so tightly coupled to HTML (it's more of an HTML generation format like HAML than a document format really) that if you need to do anything remotely complex you're forced to either inline the HTML or bind yourself forever to external tools - in which case the goal of universal readability is defeated anyway.

Markdown's syntax constrains how much it can ever do, whereas AsciiDoc is designed to be extensible, providing macros at the "language" level and underneath that there's the whole DocBook toolchain: it seems to me that the clever move is leverage all this, rather than create yet-another-Markdown (and it's not like the syntax tradeoff is at all dramatic.) I think the footnote issue you mention can be done in block macros, but I'm not sure.

I might be getting a bit utopian here, but what would be really great is if all these markup languages sought to have their canonical implementation in pandoc, which would allow for the standardisation of a set of pass-throughs/filters/annotations for things like equations and citations.

Thanks for pandoc, btw. Just out of interest, is there a reason you haven't attempted an AsciiDoc reader? (Or have you?) Assuming it'd be quite a bit more work than the others, what with macros and so forth.