Thor didn't know exactly what Diana had seen, but he also knew just from how she carried herself that neither were strangers to the battlefield. That was part of what drew him to her, after all, that ability to keep up with him and even outclass him. It was thrilling, knowing this wonderful woman had seen the worst of humanity and not lost herself to that darkness. That Diana could rise above it all was nothing but a positive.
He kept eating after she finished her food, and when she asked that question, he looked at her again so their eyes actually met. This was a story, for sure, but he wasn't going to hide it. It wasn't like the brown eye was any worse than the blue one, in any case. He had no shame about it. He just felt good being whole again, in that sense.
"This one's not originally mine." Thor said, tapping just under his right eye with the flat side of his fork. "I lost my right eye in a battle, and Rocket was able to find this implant for me."