In Swift all identifiers are Unicode - basic letters are part of Unicode. The entire source file is Unicode all the way through.
> how is a Canadian supposed to easily use it?
Using their keyboard? Can't a Canadian type these letters in the exactly the same way as anyone else would?
> In Swift all identifiers are Unicode - basic letters are part of Unicode.
Yes, and it's an exceptionally bad idea to allow non-basic letters in identifiers, as the linked article demonstrates.
>> how is a Canadian supposed to easily use it?
> Using their keyboard? Can't a Canadian type these letters in the exactly the same way as anyone else would?
No, they can't. ä, ö, ü, ß are part of the German keyboard layout QWERTZ, but they're not on a QWERTY keyboard.
Anyone can type them using a modifier key. I have a UK keyboard and to get ß I hold option and press s. It's no different to using the shift key. If you've got no problem with capital letters you should have no problem with these letters.
Sometimes I boot into a machine where the keyboard layout is set to English. Finding the right keys on my non-English keyboard to even just type "ls -l /" or similar, is a major pain in the ass. It would be the same for a Canadian having to type 'ß' on an irregular basis.
Let people who have to interoperate with multilingual colleagues settle on conventions for doing so. Let people who don't use their own language already.