So quoting Lucien Lachance "As every hand has fingers, does not every finger have a nail? A claw? A talon? Every finger of the hand, every Speaker, has such a nail."
So the four fingers(Speakers) has a nail(Silencer), but there are five fingers. On a human hand, the thumb also has a nail. Doesn't that mean the Listener should also be employing a Silencer?
Side question: The Keeper is also a member of the black hand, doesn't he represent any part of the hand?