Developer tip to save your eyes: larger fonts

Very much agreed, but not just in the editor. A big reason I like Safari (desktop) is you can set minimum font size. It also has a reading mode that is usually much nicer than reading the actual page.

Sometimes people see my phone screen and laugh at how big I've made the type, but why exactly should I want to squint at everything? I don't need the interfaces I use to look cool and futuristic, I just need to read them.

I agree that 12px is way too small. In my experience, 14px was the best choice since it balances information load with readability nicely.