Markdown is a beautiful demonstration that document structure syntax can/should be simple. What most people do in Word is better done by just adjusting the document rendering/style, not the document structure...

I love the idea of extending markdown to include more visual elements, but if you're not careful you just reinvent HTML.

Here's my personal take on extending table syntax for charts. Easy to write, and if a renderer/parser understands the syntax you get a beautiful chart, and if it doesn't you get a table with slightly weird headings:

  | Month::x | Revenue::y1 | Cost::y2 |
  | -------- | ----------: | -------: |
  | Jan      | $82,000     | $51,000 |
  | Feb      | $91,000     | $56,000 |
  | Mar      | $95,000     | $58,000 |

Nice project. But at what point does Markdown just become Emacs Org-Mode? At least with Emacs you can write Lisp to make your document do anything you want.