I'm a big Operator Mono fan. A few months ago I wrote how to Set up Operator Mono for Atom. It involves a bit of style sheet hacking. Coda is pretty straightforward, but I realized after roughly eight years of owning Coda, I've never messed with the font formatting.
Step 1: Set the font in preference under Editor
Click the Editor Font and locate Operator, select the weight you're most comfortable with.
Step 2: Setting up the italics character set
One of the best features of Operator Mono is that all its italics are an alternate character set, useful for programming. Coda doesn't pack in a style sheet akin to Atom or Sublime, which is a mixed blessing. It's pretty easy to set up but requires a little more handy work.
- Click Colors in Preferences
- Within the colors panel scroll area click on the various code examples and click the bold/italics to check boxes to change your code styles
To mimic Atom's settings and the examples on the Operator Mono website, I recommend italicizing the following: all comments, tags, variables, attribute names, and leave CSS unitalicized. That's it!