you should include quotations in your essays if you think that it is appropriate in a given situtaion....and rightly matches the circumstances
writing a quotation definitely gives you credit as it is advised by many professors of english....
if some CSP is saying that he did not added quotes and he secured good marks then he ll be right but it does not means that the same will work for you....might be he has written such a good essay that he passed without quoting even a single quote....but if you do it...it will give you credit....
i think you should prefer the views of a subject specialist over a CSP