The hiring process is a black box for a reason. The HR department's role is to protect the company first, not the employees, and certainly not prospective employees. If feedback can be interpreted as being discriminatory, or reflective of bad company culture in general, well, word gets around. For much of the time, the reason people don't get the job is that there was someone marginally more qualified/attractive/like…
I have done hundreds of interviews, and I used to do a very easy, basic comp sci test. The last question I would ask was, "Tell me about a book, cd or movie that you've read/listened to/watched that was interesting or excited you."
The point was to see if the person was engaging with the universe, not to judge their taste or anything else. You'd be surprised how many people get tripped up by this.
The worst answer I ever got was a guy who said the last album he bought was "Free Bird" (which is not an album), and was 40 years old at the time of that utterance. This person could honestly not think of one thing that excited him since then. He also ranted about Object Oriented Programming like it was a brand new thing.
The best answer I ever got, was a gentleman who was not the strongest candidate but was clearly intelligent. His answer was, "I know this is not a recent author, but I love Bukowski." And he spoke at length about his novels and poetry, and even was aware that our office was only a few blocks from where one of the pivotal scenes in one of his novels was set, and that after the interview he had actually scheduled some time away from his job to go there.
perfect answer
In my report to HR, I mentioned that he probably needed to study a little but was quite intelligent, but had fantastic enthusiasm for literature and that he was very engaging.
Of course, HR put an immediate stop to the thing with the reasoning that someone could say that their favorite book was the bible, and that could form the basis for a religious discrimination case.
After that, I declined to do interviews anymore.