User blog comment:IamJakuhoRaikoben/Chapter 445: The Ugly Fairy, Review./@comment-24228963-20150718064255/@comment-24784846-20150718190958

There was never a mention that Igneel actually fought him. Zeref said he couldn't kill him but that doesn't necessarily imply they fought. It could have been likely that Igneel didn't want to hurt Natsu.