I think one of the problems here is that people wanna share code snippets on social media, where generally, the other approaches mean linking to an external github gist or similar, which isn't as visible. I'm not sure if I see a good solution, other than suggesting that the "link previews" for social media sites display the code snippet inline, if it's a link to a pastebin/github gists page.

Edit: Perhaps something can be done by somehow embedding the content into the image (EXIF?) Metadata?