Bill,
Parabolic's post implies two things which are false.
First, that it is not possible look at a large group of photos grouped by category and tell a difference because of the abilities of the user.
It is actually because of the errors of non professionals that a larger selection would be more helpful. How are you going to make any judgments if you only took photos from the top ten UW photographers? Low ability users help to identify faults and which cameras can better compensate for them.
Second, that you would not be able to tell the difference between a group of images from a high quality camera and a low quality camera.
"If you could find a group of galleries of underwater photos sorted by camera, and if they contained a large number of images taken by a large number of photographers, the galleries would all look the same."
Sorry, but again this is utterly false. Can anybody with even marginal eyesight not tell the difference between a SeaLife DC200 gallery and a Nikon D700 gallery?
All three of you have implied that it depends on the abilities of a user. But it is because of this that it is more important for someone with less skill to find what type of camera suits their expecations.
Professionals can talk composition and whatever else they want all day long but if the beginner is simply looking for a camera that does a little better in poorer lighting situations, or has a little sharper focus because they are going to take "closeups of cool thingy's underwater" without knowing the plethora of skills everyone else has honed in order to professionally market their shots, then a large gallery for comparison can be very helpful.
It's not a matter of what professionals consider to be a quality photograph, it's what type of attributes that person is looking for, and if later on they want to dive into the deep end of somebody's UW photography clique then so be it.
Like I said in my first reply, maybe parabolic meant something completely different from what he wrote.
Cheers