‘Really, our opinions were so exactly the same, it was quite ridiculous! There was not a single point in which we differed.'

I can't help thinking of a couple connetions with this. One is the opening guns of Marianne and Willoughby's realtionship, how she is deceived into thinking that "their taste was strikingly alike." The other is Mr. Collins boasting the he and Charlotte were of one mind about everything and what a perfect partner she was for him, never knowing how he's being guided by her. This seems to be a favourite keynote for Austen to indicate that there's a deception of some sort in progress.