I don't think parent is talking about other file types exactly, but rather that on github itself, you can have code blocks within your .md that get syntax highlighted. Which, for some people, is a pretty key feature of github markdown.
On yours, as in parent's example, the code blocks don't even get put in a `<pre>`, which would be the minimal 'right thing' if you're not going to do syntax highlighting.
(Of course, yes, syntax highlighting code blocks within .md is pretty much going to use the same logic as handling other file types, it's true).
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.
Fenced code blocks do come through as expected — complete with syntax highlighting. Well done!
One suggestion though: I expect my code blocks to not wrap — they’re in <pre> tags, after all. The stylesheet should have them rendered either with horizontal scrolling, or with overflow.
On yours, as in parent's example, the code blocks don't even get put in a `<pre>`, which would be the minimal 'right thing' if you're not going to do syntax highlighting.
(Of course, yes, syntax highlighting code blocks within .md is pretty much going to use the same logic as handling other file types, it's true).