Does anything need all those features though? If you need more than headings, bold, italic, quoted text, and code, you should probably be using HTML or Latex or something. So a better goodness-of-fit function would be is it easy to remember/use, and is it non-intrusive inline with the text?

I don't think anybody needs all of the features at once but people have different preferences. E.g. I typically do well without bold formatting (I only need one level of emphasis which is served well by italic) but I want tables, links and lists very often.

Also I like the WYSIWYG feature of Markdown where it has an advantage over the traditional Markup languages like HTML, LaTeX, groff etc. of being easier to read in the text file. Dedicated syntax highlighting can go a long way to make markup easier to read, though.