Adopting a considerate approach, it's important that they understand. Whether or not they can understand what is being said doesn't matter; as long as communication is established.
In my experience, when I see a call sign with my eyes, my brain automatically reads it as "2". When communicating over the radio, I always say "two". Having one Chinese character mixed in among five letters is too awkward and unnecessary.
Can alphanumeric strings appear in ATC communications? If not, there would be no controversy.