Well, I to be honest find that the lack of Japanese in some martial arts in Australia is annoying. We have a most laid back attitude towards things that there is often very little respect for other students or for the instructors. The relaxed attitude also has some people often forgetting to bow before getting on the mat or entering the dojo (in fact at the last dojo nobody EVER bowed at the door). So you have the elements of respect to think about. Too often if you slacken the respect youll get people going "oi you" (meaning 'sensei') and it often helps to remind us idiotic full-of-ourself westerners where we stand... the instructor is respected, so use a term of respect at all times.
I also know many Judo throws incidentally... and it is very annoying when talking about a "Stomach Throw" to a Judoka and them having no idea what im on about, after much explaining the throw being told "OH! Thats 'tomeo nage'"... so yes the problem of communication is an issue. Also the point that these arent Japanese words for English things, the English words we fix to a Japanese word is ONLY AN APPROXIMATION. Therefore a scabbard is NOT a saya, a saya is the scabbard of a japanese sword... and what is a japanese sword? a "sword"? or a "katana"? You have swords from all around the world being called by their traditional name, why dont we just call them all 'sword'?
I have also done some Wing Chun Kung Fu and they use a lot of bowing, chinese, 'sifu', 'sihing', 'dailo', 'pak sao', 'larp sao' etc. they call each other brother/sister etc in chinese.
And does it need to be reminded that martial arts isnt just about killing people? We all know martial arts is just about death right?... oh excuse the sarcasm..hehe .. yes, culture... what a thing, your learning a part of Japanese culture when you learn a Japanese martial art, the Japanese language is also a part of Japanese culture right??? So in other words its not "lets try and make this as Japanese as possible just to be cool" its "lets keep this as traditional and culturally accurate as possible whilst still being possible to learn in our country".
Also, if I am not mistaken -kun is male specific? And why would you call an instructor -chan or even -san? All teachers in Japan are -sensei. Its also more proper to use someones last name than first name using most of those endings apart from the friendlier ones (since when your friendly your on first name terms with people). Again its just respectful, respect being a part of Japanese culture and something western society would do well to learn about.
Sorry if this post has a rather annoyed note to it but I am getting rather annoyed as someone who studies Japanese and Japanese culture when I see their culture dying away and become westernised. I am getting annoyed with how western countries are trying to tell everyone that they know best and that every other country should become westernised. *sigh* Here we come world where no nation has its own identity and all culture throughout the world disappears.