I think the point is that the issue is not only language, it is more really a matter of culture. For example, in many, if not most, European countries in the countryside, it is normal to say good morning or good day when you pass people. The language is not so important. So, an Italian passing a Frenchman might say buongiorno or an Englishman in the same situation could say good day. It is saying the greeting that is important, not the language.