He was wrong to continue and Norland, and to show up at Barton cottage. He was wrong to allow the attachment to form. So I guess I concede and can call it unprincipled. But I still would not place him near Willoughby in the continuum of unprincipled behavior.

I think perhaps Elinor's forgiveness of him is evidence of a selfless kind of love. How long is the appropriate amount of time for her to hold a grudge? She has decided that he meant no harm to her, and so she is able to forgive easily. Yes, her being in love makes her more inclined to forgive easily. But even if she found out he was sporting with her, eventually she should forgive anyway, right? Just because someone may be forgiven, doesn't mean you should forget. Elinor would never allow herself to be put in that situation again.