Turns out, you can use Cloud.typography fonts on here, and doing it isn’t too difficult.
You’ll need to edit the CSS of your theme. Copy the URL from the code that Cloud.typography gives you, and insert that into an @import statement. Then change the font-family to reflect whichever font you chose. In my case, I’m using Whitney.
@import url('https://cloud.typography.com/…/…/css/fonts.css');
body {
font-family: 'Whitney SSm A', 'Whitney SSm B';
}If you have any questions, let me know!