This was never an issue until the random dungeon finder, but at that point anyone using macros or perhaps simply %t in a chat will get a message like this.

"blahblahblahblahblah Usul-Madolan" IN ENGLISH (the target name in English)

However other members of the group would be like "美女-大山” this invariably gives away the fact we are using English clients and often creates party banter as everyone sees the English used for my name (THE SERVER NAME IS IN ENGLISH) while everyone only sees Chinese for other people. (THE SERVER NAME IS IN CHINESE FOR CHINESE CLIENTS) This is not "I see English for me, and they see Chinese", they do indeed see the English for my name.

Also, for some reason it says Madolan instead of Madoulan, something I found odd I think it's supposed to be "dou".

I'm not sure why this is, or if anything can be done about it, just pointing it out for those who might be interested.

Yeah, that's an annoying issue. That's also why we can't whisper ppl in battlgrounds unless you know the english translation of the chinese realm name. (but chinese client users can whisper me just fine so I wonder).
Tho out of hundreds of dungeon runs I might have heard a remark 2-3 times only.

Somehow our client is broadcasting the names in english. Maybe there's a workaround modifying a mpq file. Will see if i find it.

As for showing you are using an english client I wouldn't worry much as long as you are buying your card.