The formulae are indeed stored in the same format, regardless of language. For rendering and parsing in the UI they use translated function names and the field separator (commma in English, but semicolon in many other languages because decimal numbers use a comma there).

It does irk me a bit (though not as much as the translated VBA back in the day). But that's probably because I know English, I often look for solutions to my problems in English, not in my native language, and then would have to mentally translate that back. But that's perhaps a burden for programmers more than for typical users.

A few thoughts:

• it's been that way for decades, at this point. So changing it would annoy a lot of users

• the problem with comma and semicolon would remain unless you want entering numbers normally and within a formula to be different. I'm not sure that's good in a product built around numbers (and often numbers that should be written and formatted like any other number in that country).

• making it configurable might work, but that then requires more testing, although sometimes it's not clear how much testing Microsoft is still doing, so that might not be much of a point. But adding options also has UX limits and not just in the length of the settings screen.