This week I finally sat down and spend some time with Markdown input and output. Both saw major changes. Markdown input was bumped to upstream version 2.0. Output was completely rewritten from scratch. Markdown output is now completely custom code (not using a third party output module like before). I based the new markdown code off of the Textile output classes I helped Perkin to create.
As with all new code and major changes there are probably bugs. I tested Markdown output with a variety of test material and kept working at it until everything converted acceptably. I also used a variety of the Markdown tests provided by John Gruber to ensure my output was correct. When converting the HTML output tests back to Markdown the output is similar enough to the original that I feel it is acceptable.
The last big change I made this week was adding a new OEB transformation to unsmarten punctuation. As the name implies it changes curly quotes, apostrophes and a few other characters to their plain text, straight equivalents. It basically does the opposite of smarten punctuation. I find this especially useful when converting to formatted (Textile or Markdown) plain text files (TXT).