I tried this, many years ago, but it did not take long before I gave it up. Code is full of skinny punctuation characters whose meaning is critical to understanding, and allowing a proportional font to squish down the screen area they occupy does not improve readability. This can easily be seen in the author's own screenshots.

Nope, no thanks.

Space indentation after text is very much a thing for me, and proportional fonts break that. Monospaced text looks neater to my eye, as well, and when I’m trying to figure out “how the hell that ever worked”, I don’t want the cognitive dissonance of trying to ignore the unaligned text.