[Jach]

I almost entirely agree, though I think your third point (typing non-ascii characters) could be less severe with one extra lesson in the typing course most kids are forced to take. When I first took French in 7th grade somehow I learned online you could enter ascii codes (whatever those were) on Windows with alt+numpad, and I still have memorized that alt+130 gives é. Later I moved to Linux where we have a great Compose key system, so I can just type <compose> + e + ' and get é, <compose> + c + , to get ç, and so on, with <compose> mapped to whatever I like (currently right-alt). Supposedly (haven't tried it) this system now has a Windows port: https://github.com/samhocevar/wincompose

Asian languages are harder. But if you're told about IME, then at least if you know what you want to type, how to actually type it isn't a big burden. IME can also help with rarer math symbols like ⋂ (\bigcap) ≅ (\cong) or ⊵ (\unrhd), or is another way to get something like the compose key system.

[BiteCode_dev]

That's a recipe for combinatorial explosion: each language has special chars or even are just made if glyphs, are you going to learn them all? Do you want to impose the burden for all devs in the world?

And now your typing is not at all fluid, even if you didn't have to stop and thing about every single special characters (which most people do), you will have to enter a combination to get them every time completion can't help.

In fact, even with an AZERTY keyboard, typing French, my native language, is slower than english.

Instead of having one simple common ground, you also now have an infinite number of variations to care about.

Not to mention having to understand a lib in spanish, an another one in russian and a last one in Hindi or arab.

[Jach]

I don't need to learn them all, I just need to know the ones I expect I need to type in for the foreseeable future. I might even forget them later (as I've forgotten a lot of LaTeX mappings, fortunately there's a cheat sheet).

You're just repeating your other points about the problems that come from having so many languages, which I mostly agree with, but typing at least is not really an issue, which is all my point is. The issue is: "do I know Arabic?" not "I know Arabic, can I type it?"

As for your experience with French, maybe the AZERTY layout is just inherently bad, but how much slower is it really? Typing your example sentence with my compose key takes me about 3x longer than ignoring the accented characters entirely, which is more than I expected, though I'm very unpracticed. With Japanese, which I'm even more of a noob at, nevertheless the overhead is smaller. If I wanted to type 'purple', I hit a chord to enter JP IME mode if I'm not in it already, type 'murasaki' (the romanized version of the word) at full speed, and leave it as むらさき or select from kanji completions to get 紫 or maybe I needed it to be in katakana so I hit F7, finally I commit it and move on. It may seem like a lot but whatever the case it's a really tiny overhead from just typing 'murasaki'. In practice though looking at source code from Japanese developers I see a mix of full English (maybe some Japanese comments, maybe not), some mix of Japanese but always using romanized symbol names, and full-on variable and function names are in actual Japanese. Because the overhead of typing is so small though, I don't have a preference for the second or third option, they're both fine, though of course selfishly I'd love for the whole world to understand and use English exclusively. For the French case, even with an overhead of 3x in the worst case, I wouldn't object to a variable with an é in it.

[BiteCode_dev]

I know a lot of devs that don't even type with 5 fingers, you are apparently well trained with your keyboard and you take a X3 hit.