"use syntax highlighting" is really a poor defense. I'd say that code that isn't readable without syntax highlighting is just that: unreadable. One doesn't always have the luxury of using the editor that's tuned to your preferences - you may be looking at someone elses screen. Or you're debugging some code on a box that only has vi. (And when I mean vi, I mean vi. Not some vi clone renamed to vi). Or you may be reading code outside an editor (more, git blame, ...). Some people don't even have the luxury of easily distinguishing between colours - or they need the black-on-white constrast; any other colour just won't do.
I always write my code assuming the next person looking at the code uses ed and a 80x24 glass monitor, knows my address, and is a sociopath who keeps his axes sharp.