WHEN IS A MARQUIS NOT A MARQUIS?

In the case of the Marquis de Sade.  He wasn't a marquis, he was only a comte.  The title of marquis comes above comte and I fear yon comte was no marquis.  By the way, in English the spelling Marquis is sometimes used, but the spelling Marquess is preferable.  The equivalent in the English peerage of Comte (which is translated as Count) is an Earl.  This is why an earl's wife is styled a Countess.

Now there's a soupçon of unsought information for you.