User blog comment:IamJakuhoRaikoben/Chapter 503: The Last Sight Seen, Review./@comment-5303512-20160926122525/@comment-2214433-20160926130633

Based on this chapter alone, Natsu didn't change his personality at all. It's his very basis to go look for Zeref. He's an Etherious. Otherwise, he'd not leave Lucy unhurt and would not recognize Gray.