Face lightening is only showing what may be seen in real life and as such is acceptable to me. Changing the iris hue, colour, saturation or anything else that makes it substantially different from real life wouldn’t be acceptable in certain uses such as photo journalism but otherwise why not?
The text mentions “legitimate”, and I would ask “in whose eyes?”.
It’s the intent or purpose of the photo that matters, and if someone adjusts an image, provided that it is done with the victim’s approval, then I don’t think it usually matters one way or another. Personally though I’d draw the line here –