對於演奏者而言，不同時期、不同風格的作品，要求他在指觸、用力、踏板、音響、分句、呼吸、速度、力度、色彩、裝飾、結構、層次

On the surface, this statement seems correct. If this statement is meant to point out extremes in musical interpretation (such as 一首雄壯的歌,被奏成哀怨的感覺), then you are right. If this statement is meant for a 5-year-old beginner playing Book One of John Thompson, then you are absolutely right.
However, that is not what you are talking about; you are talking about 演奏者, or a concert artist. To a concert artist, interpretations are not always so extreme. How do you define 不合適? For little kids or beginners, 不合適 means extremes: 雄壯 and 哀怨, happy and sad, black and white. But since you are talking about a professional performers, "不合適" could mean very small nuances. Most of these small nuances are, I suspect, not discernable for average listeners. These small nuances or variations in interpretation could bring about new colors and lights to a composition, and, in my opinion, definitely not 更糟糕的錯誤. Sure, if you are talking about playing a little piece in John Thompson; but let's say we are talking about some of the Bach Partitas or the late works of Brahms or the Diabelli Variations, 不同的聲音、速度、力度 could actually bring out different aspects of the musical work. Please definte what is 不合適?!?!!!
One question to PianoProShop: since you are a teacher too, are you teaching music (with creativity, innovations, attention to minute details, etc.) or mathematics (one answer to every equation)?
This kind of thinking is what makes Hong Kong people so un-receptive to different performances of the same music. People here are taught one way of playing, one way of thinking, and they think that what they know is the only correct way. Teachers are unwilling to accept or explore different ways of interpreting a score. Music is not about extremes (we are not talking about John Thompsons here, right?). Music is about expressing each performer's living interpretation of a dead score. So what if I play Bach with a bit of romanticism, or play Rachmaninoff a bit dry and cold? Am I wrong? Am I 不可容忍? Is it 不合適? Who are YOU to make all these decisions for us?

Now this is a professional answer from a true professional.

我很同意樓上那位說的。
怎樣才是一個「合適」的演繹？音樂是沒有絕對的，你認為這是對的演奏，我卻能說這是不可容忍的「戰略錯誤」。
用另一種表現方式來演繹一首歌，或許能讓人有耳目一新的感覺。

呵呵
舉個例
一首雄壯的歌,被奏成哀怨的感覺
十分怪異~
這就好比不尊重作曲家一樣

彈錯音、背錯譜
這點事係一d小錯,人誰冇錯
但用不合適方法來演奏一首有特定風格的樂曲
就不可原諒~

Yes,I agree.