> actually quite easy to solve

I cannot square your earlier assertion that we should be more mindful "that not everybody writes in English", with your current assertion that all code must only ever contain English, for simplicity's sake. Either is a cogent position on its own, just not both at the same time.

This bug arose because the programmers made incorrect assumptions about the result of a case-changing operation. If you impose English case rules on Turkish symbol names, this exact bug would simply arise in reverse.

More problematically, as I alluded to earlier, Turkish code may contain a mix of languages. It may, for example, be using a DSL to talk to a database with fields named in Turkish, as well as making calls to standard library functions named in English. Which half of the code is your proposed invariant locale going to break?