Difference between Cantonese and Mandarin: using 係/是 to link noun with adjective? This Chinese grammar page states 


  是 (shì) is only used to link two nouns. It cannot be used to link a
  noun and an adjective.


For instance, you should not say this in Mandarin: 我是高

But in Cantonese, it seems like you can say 我係高, and it would be considered grammatically correct. This seems like a common way to emphasize some quality as in Yes, I *am* tall.


Is the grammar page correct, that is you cannot use 是 to link a noun and adjective?
If the grammar page is correct, does this mean Cantonese and Mandarin differ in this regard, or is it wrong even in Cantonese to say 我係高?
我(高)是高 in Mandarin and 我(高就)係高 in Cantonese are both common phrases. They are always followed by a contrasting statement 


Simply put, you have to follow "我是高" or "我係高" with a "but"  

Example:

"我(高)是高, 但還沒高到可以打職業籃球" (I am tall, but not tall enough to play pro basketball)

Same goes to Cantonese: "我(高就)係高, 但仲未高到可以打職業籃球" (I am tall, but not tall enough to play pro basketball)


  Both "我是高, 因此可以打職業籃球" and "我係高, 高到可以打職業籃球" are grammatically incorrect because there are no contrasting statement. 


One difference:


  "我高是高"(It is true that I am tall) is not usually reduced to "我是高" in Mandarin , even it is not technically wrong;  on the other hand, "我高就係高" is routinely shortened to "我係高" or even "我高" in Cantonese"