[tannhaeuser]

Interesting, didn't know about <!DOCTYPE markdown>. Though as an SGML pedant, I have to say using this doctype declaration in this way just tells an SGML or XML parser about the base ("root") element and is thus simply incorrect since there is no "markdown" element. The proper way would be to use just "html", and adding SGML shortref declarations in the "internal subset" for markdown-to-HTML mapping, like sgmljs is doing.