Dickens was only calling the guillotine by the nickname the French mob had given to the device during the Reign of Terror. They called it Madame la Guillotine. Of course, in the French language every noun has to be either masculine or feminine. Perhaps it was felt that the name sounded somewhat feminine because it ended in ine. Does la guillotine or le guillotine sound better? Perhaps the intention was to distinguish the device from the old chopping block (hachoir) which is masculiine. The idea of naming such a terrible instrument Madame was characteristic of French humor. It was a way of suggesting that it was gentle, delicate and compassionate, when it was just the opposite. Dickens was only adding a touch of local color to his novel by borrowing the nickname from the French. There is no anti-feminist implication. Half the nouns in the French language are feminine of necessity.