At the end of Chapter 16, Edward arrives for a visit. He had not written that he was coming, which seems a little rude to me, but perhaps that was not unusual for the time period?

More interesting is that he has already been in Devonshire for 2 weeks, staying with friends at Plymouth. Since he was coming to this part of England anyway, a short note to the Dashwoods to say he'd like to stop for a visit would have been polite, imo. And why was it that "[he]e looked rather distressed as he added, that he had been staying with some friends near Plymouth." Why would that be a big deal? Or is the narrator just giving us Marianne's impression here, since his response was to Mariann's surprise that he had been in the area that long a time?

I don't take much stock in the fact that Marianne thinks that Edward "was confused, seemed scarcely sensible of pleasure in seeing them, looked neither rapturous nor gay, said little but what was forced from him by questions, and distinguished Elinor by no mark of affection." This is, quite simply, Marianne's opinion of everybody who doesn't act the way she thinks they ought, and especially her opinion of a man (supposedly in love) who does not act like Willougby.

Elinor also finds Edward not acting like he did, however:

His coldness and reserve mortified her severely: she was vexed and half angry; but resolving to regulate her behaviour to him by the past rather than the present, she avoided every appearance of resentment or displeasure, and treated him as she thought he ought to be treated from the family connection. [emphasis mine]