The specific person you briefly mentioned, was actually able to converse easily in English, plus as @Macgyver15 pointed out, others haven't cursed Anker (as I've said before, I do use swear words, but I dont swear AT Anker (in the collective)).
I think having English as the rule for the default language is correct.
Anker in Asia have their own thing. That's the only area where English isn't taught generally. Whereas almost all European and southern America, Africa, are taught English in schools.
English is the international language of business (not just because of USA either). Many many years ago, it was french, and biblical times it was Greek (you thought Roman didnt you!).
I understand how you may want to compromise, but there needs to be a fixed language. Otherwise madness can ensure.
It's great that lots speak other languages, but the vast majority don't. So to have an open forum/community, we need one language and no more.
I do ask others who have written in non English, to correct it. To be fair, most who do speak other languages, do ask the poster, rewrites in English,and that English is the language of here.