Astonishing chapter, really. So picturesque and powerful way of setting the pieces between Charles-Henri and Marie-Joseph. I don't get the confusion. Obviously neither the dance, nor the actual conversation happened, but it's a way to remind us where they stand and what they represent.
Charles-Henri bloomed, instead of wilting, when he was used by that whore. There's more confidence in him, he's more ready to act and he did not change his goal - the world where executioners are not needed anymore. A world in which pain is quick and dignified, instead of full of blood and suffering. It'd seem - not without reason - that he thinks this part of culture also shapes their society. This fixation on executions and on making them spectacles.
That's what he's aiming to change, one step at a time, using his own means, as Monsieur de Paris. If anything, him and Marie becoming rivals is a very welcome change from Marie just hating her brother for betraying her trust and being "like everyone else".