appreciate 表示“感谢”时，其后所接宾语习惯上只能是指“事物”的名词或代词，而不能指“人”的名词代词。若要接指“人”的名词代词作宾语，可以用动词thank 等。请看：

他环视四周，看看有多少人能理解他重口味的幽默。

正：His eyes roved to see how many of the group appreciated his heavy humour.  

误：His eyes roved to see how many of the group appreciated him for his heavy humour.

我感谢他们长期以来忠诚的效力。

正：I thanked them for their long and loyal service.

误：I thanked their long and loyal service.