Since it's mostly a good-faith rule to begin with, it seems easy to add something like, "unless you are using it as an assistive technology for accessibility reasons".

Yes, and that's the case with all the rules. I don't want to say "you should break them when it makes sense" because if I do, someone will post "Tell HN: dang says break the rules". But the rules are there to serve the intended spirit of the site—not the other way around. If you're posting in that spirit, I would hope we would recognize and and welcome that, not tut-tut it with rules.