I wish they would just make HTML previews work instead of hardcoding specific use cases with 3d models and geodata.

Eg why can't github just let visitors preview this html file: https://gist.github.com/dergachev/5769111#file-index-html

For now, I have to link bl.ocks.org, which is nice but far from perfect. And check out http://htmlpreview.github.io

(I understand that there are security concerns, but I'm sure they can be addressed with an iframe or by clicking an external link)