Uncle Pug once bubbled...
First principle: Test everything... hold on to that which is good.
It would be extremely unwise IMO for folks to just take advice given on any board without due care and caution.
It would also be unwise to reject out of hand any and all advice simply because it was give on an internet forum.
(btw... you shouldn't believe advice given in person without critically thinking it over either.)
So how does one determine the validity of advice given here on Scuba Board?
Well for starters consensus is a good clue. If you find the same advice given by multiple posters then that can help.
Secondly you should try to discern the actual diving experience level of the advice givers.
Thirdly... track record. Read back through the poster's history and see what kind of advice they have given in the past. You will also find clues as to what kind of diver they really are.
Those who are new to the board might claim credentials but until they have a track record it is difficult to know if they are who they say they are.
Again the guiding principle should be "test everything and hold onto that which is good."
A former president said it best "Trust BUT Verify"
But I entirerly agree with your points. More then anything else I use this board to see what the general thaughts are out there regarding diving. I would never make a decision soly based on the feedback on this board or any other Internet forum for that matter.