Use of demeanor with plural subject

Question

Consider the following sentence.

I was studying the faces and demeanors of the people in the hall.

As the subject is plural, the author naturally used demeanors. However, I believe it should be demeanor, but I can't actually explain why (or find anything to support my belief).

Can anyone enlighten me on that?

Answer 1

Wikitionary lists the word demeanour as both countable and uncountable - meaning that both demeanour and demeanours are acceptable.