So you love the Operator Mono font? I don't blame you! So do we! It's a bit pricey but worth every penny.
In fact, we're so used to it in our editors that we were a bit sad with GitHub's otherwise neat code views. When we review PRs in the web UI, we want our Operator Mono!
So, assuming you have it installed on your machine, you can put the JS bit in the other code snippet of this Gist in a bookmarklet, and click it when you're on a GitHub.com page you want to have switch over to our beloved font. We used the ScreenSmart variant here, which you get in the font package and have probably installed, as it's the more legible one on screens. Feel free to adjust the font name if needed.