I agree. (:D) I don’t think Edmund saw the pun in its worst light. If he had I think he would have thought it coarse and that Mary was vulgar to say it. When he said Mary was not coarse he was speaking of her countenance and manner:

“The right of a lively mind, Fanny, seizing whatever may contribute to its own amusement or that of others; perfectly allowable, when untinctured by ill–humour or roughness; and there is not a shadow of either in the countenance or manner of Miss Crawford: nothing sharp, or loud, or coarse. She is perfectly feminine, except in the instances we have been speaking of. There she cannot be justified. I am glad you saw it all as I did.” (7)