[gbrindisi]

Medium allows you to set a canonical tag, so authors can direct SEO juice towards their own websites. Github/gist doesn't have that.

In practice 99% of what you read on Medium is syndicated, they are in the business of trading an audience for content (that in turn will grow their audience).

[XCSme]

But then why does the Medium article still have better SEO than the original one? You are still directing more traffic to Medium instead of your site.