Hi Mark,
All you can (or should) do is use the "Contact the Photographer" link on the photo and send the person a private e-mail to point out your concerns. If the person is like most photographers, and has pride in his/her work, the problem will be fixed, and the person will likely appreciate the fact that you kept the errors between you and them. If they don't fix it, there is nothing more that you can or should do. Errors or issues with other people's photos are between them and the Admins.
With regard to posting public comments about errors or flaws in some other person's work.....I fully support Admin's approach in rejecting such efforts. It's just not a very kind way to treat a fellow enthusiast to point out his or her failings in public. Always assume that the person cares about the quality of their work and contact them back-channel. If they do not respond, then MYOB is the best policy.
