I came to this GR just a few days ago and after reading (nearly) all of your posts, I realized that this hasnīt been discussed yet - John Thorpeīs way of talking.
This is my second reading of NA and every time Thorpe is introduced by the narrator my first impression is: "What an awful way of talking that man has. He surely canīt be trusted."
Am I the only one who loathes that? I also wonder that in JAīs time a wannabe-gentleman uses "Oh, d it!" in every third sentence. Surely that must have turned others off, donīt you think so? And I also wonder why Catherine doesnīt distrust him from the beginning. The reasons might be - as others have pointed out before me - that due to her brotherīs friendship with Thorpe and her acquaintance with Isabella her judgement was restricted...