When I insert one of my gists with Unicode characters in it (e.g. this one) I get a Liquid error:

Liquid Exception: incompatible character encodings: UTF-8 and ASCII-8BIT

After a bit of debugging it turned out that the contents of the Gist is not encoded right, most probably because github itself doesn’t send a Content-Type header or any other means of specifying the encoding of the raw Gist.