I like Markdown, and generally agree that it strikes a nice balance between correctness and usability...

...but it's delicious that this blog post also demonstrates an ambiguity in Markdown: how to handle intra-word emphasis. In the rendered output, "mark_up_" and "mark_down_" were probably intended to be "mark<em>up</em>" and "mark<em>down</em>", but the underscores were instead rendered literally.

I do appreciate that Markdown's solution to ambiguities like this is dead simple - just inline some HTML.