User blog comment:Paper Lantern/I blame Duncan/@comment-1037137-20130829000852/@comment-1756703-20130829003557

Agreed. A common argument made by DxG fans is that Duncan was fed up with Courtney's attitude. But like you said, during the first two seasons, he actually enjoyed her feisty and bossy attitude, even to the point where he found it attractive. That's why his sudden distaste for that aspect of her personality in TDWT made no sense, and seemed to come out of nowhere. His betrayal of Courtney was completely nonsensical.

Also, I don't blame Courtney for reacting the way she did in TDWT after she learned of the affair. Gwen and Duncan showed no remorse for it, and Courtney needed vindication for having her heart broken so callously.