Another GitHub nuisance:
I'm a huge fan of pinboard.in and use the Firefox popup bookmarklet quite a bit but github repositories [1] won't let me bookmark them with the bookmarklet. GitHub repositories are literally the only pages I've found the I haven't been able to use the pinboard bookmarklet, and it's been that way with every single GitHub repository I've tried to pinboard.
The bookmarklet fails due to GitHub's content security policies[0], which disable inline scripts. I'd suggest installing the Pinboard browser extension to get around those limitations.
[1] Strangely github.io pages bookmark just fine.