User blog comment:FairyRaven/Fairy Tail Chapter 401: Igneel vs. Acnologia, Review and Commentary/@comment-77.194.131.12-20140922125827/@comment-31.61.131.139-20140922142219

First he hang out with them for some years, and he planned to destroy them, so I would expect him to gain as much information as he could. Second, Gray's eye thingy used on Tempesta seemed to be like a scanner or something, providing him information.

Of course it is not proving anything - more like hinting towards. The whole situation just seems kinda suspicious to me.