Sorry, I was confused. What I meant was actually responsive design on the "desktop" site, perhaps instead of a separate mobile variant.

I really prefer to zoom in on most website to get bigger text, and good responsive layouts often become less cluttered when you zoom. GitHub's widths are too static though so everything just overflows.

I kind of like using the mobile version but it's annoying to have to spoof the user agent and all features aren't available there.