It's more casual conversation than anything else. If Marinette realized the carnival was inter-dimensional she'd be surprised to meet someone else with a French name. As a Parisian, French names are just normal to her and she doesn't think to question Delacroix, except for the fact that it's attached to a bird.

"You're from Quebec?" She didn't know much about Canada, but she assumed she'd hear an accent if he wasn't from France. Then when he says his French is rusty, she's even more confused than before. They were both speaking French, weren't they? But actually if she concentrated, really focused on the noise around her and paid full attention to the words, she could tell that the people around them weren't all speaking French.

"Are we speaking different languages?" she asks, suddenly looking shocked all over again.