It looks like he just fed it a plain python gist, no Markdown, no nothing. On the site it says the service can be used "to elegantly share gists written in Mark

It looks like he just fed it a plain python gist, no Markdown, no nothing. On the site it says the service can be used "to elegantly share gists written in Markdown", so I don't know why he would expect that to work. I guess a clear error message would be helpful, but then you would either have to rely on everyone using standard file endings, or do some pretty fancy (and unreliable) parsing to determine if it's actually Markdown.