Sure, you could consider it unprofessional, but I'd wager that the large majority of all professional programming is done in languages other than English. The tooling issue is an "is vs. ought" problem. In 2019 full UTF-8 compatibility is not a feature anymore; on the contrary, a lack of support is a bug.
Do you have any citation on that ? From what I know the vast majority of all professional programming is done in English. Even companies like SAP that had a lot of programming in German have shifted to programming in English.
