At the end of the 19th, beginning of the 20th century there was a school of thinking in psychology called Structuralism. To oversimplify greatly, they attempted to formulate an objective vocabulary to describe subjective experience...that is, a way to describe a sensory experience using language in such a way that another person could replicate the experience. They failed.
In many ways, audio reviewing has become a new sort of Structuralism. We hear a piece of equipment, and try to find a set of words that will convey to others our experience with that equipment. However, even at best, we can only approximate. We are likely to do best with people we know, who have listened to the same setups as we have, and heard the language we use to describe a particular sound that they have experience personally.
If vertigo says a piece of equipment sounds veiled, does he mean the same thing that I would, using the same words? I doubt it. That doesn't mean that one of us is wrong, it simply means that we really don't have a vocabulary for communicating all but the barest outlines of our sensory experiences. Fortunately, that is usually enough.
I've heard veiling with the HD-600, which has always been a good sign that something was wrong upstream. Fix the problem, and it went away. IMO that is one of the HD-600's strengths, as well as a weakness. It doesn't lie to you, and it is not very forgiving of any weakness ahead of it in the audio chain.