Please dont take this as criticism and just a question:
Why native English speakers like so much to shorten words so much? To me, a non native, a11y reads like ally and in no means reads accessibility. Any tips on that?
It's not a native English speaker thing, it's a cool tech i-don't-have-time-to-waste-writing-words thing. Outside of the tech world no native English speaker would have any idea what a11y was supposed to represent either. We do love shortening words but usually in a more natural way.
I suspect it's basically "wanted shorter terms for things that couldn't be turned into an acronym" because ... well, because we're lazy and like typing less.
Though i18n for internationalisation has been around for so long now that when I see something like a11y or k8s or etc. I assume it's Another One Of Those and go find out what the long version is.
You do need a font where 1 versus l is obvious, but that's also true of reading code so most of us probably -do- have such a font already.
(I can see why it's confusing; all I can really say is "you get used to it eventually" and possibly "sorry" ;)