Brent Roose wrote down his thoughts around how things like fonts, spacing, docblock, ... can influence the cognitive load of a programmer.

As a professional programmer, I'm reading and writing code on a daily basis. I'm working on new projects, doing code reviews, working with legacy code, learning documentation etc. Based on my own experience and that of colleagues, being a programmer often involves a lot more reading than actually writing code. Whether it's your own code or that of others, when you open a file, you have to take it all in. You need to wrap your head around what's going on, before you're able to write your code. Doing this day by day, it's important to find ways to make this process easy. To try and reduce this cognitive load as much as possible. Streamlining the way you take in code, will allow you to not only work faster and better; but also improve your mental state and mood.

Visual debt is real.