He also wrote what I suspect is the de facto Markdown parser for Racket, which is used in Pollen. (I thought I recognized his name dimly, and it's because I reported a bug in Pollen a few years ago relating to Markdown smart quote handling that turned out to be a bug in his Markdown processor -- which he fixed virtually instantly. https://github.com/greghendershott/markdown/issues/45 for the curious.)