A lot of programs break on Polish computers when you name your user "Użytkownik". Android studio and some compiler tools for example.

When I was at Microsoft, one test pass used pseudolocale (ps-PS IIRC) to catch all different weird things so this should have Just Worked (TM), but I was in Windows Server team so client SKUs may have been tested differently. Unfortunately I don't remember how Program Files were called in that locale and my Google-fu is failing me now.