Is "itu" usually used when one is referring to a characteristic in general?
It sounds strange with sabar, but with teman the difference is clearer. Teman baik = good friend. Teman itu baik = that friend is good. I think sabar baik would more closely mean good patience ... which sounds weird in English and, my wife tells me, also sounds weird in Indo.
if i may, i think your example is wrong :)
The correct example using " Teman itu" (following the same pattern with the sentences above) is
(ber-)Teman (stop) itu baik
Friendship is good
The one you use is:
Teman (yang) itu baik
That friend is good
Yes, I understand, although what I was attempting to do wax show how itu changes the meaning, and hence, how removing itu from the given sentence also changes the meaning. My explanation could definitely have been clearer.