I'm not sure I agree. Ears can be fooled without proper training. That makes experienced reviewers (even biased) better suited than a body of dull amateurs. Quality over quantity. Over time you can judge a professional reviewer. You can easily rig any poll by posing the wrong question. As the topictitle shows.
You talk about variables, I see it more as pieces to a puzzle when it comes figuring out who to trust. If you know the viewpoint of a reviewer you know how to interpret what he says (and fill in the blanks). So you turn the piece around and it fits the picture.
You mention things that can influence 'information'. No, it influences data. Systematic or tandom errors. When you properly corellate the data you obtain information. But the bias of those reviews is more malicious. It feins objectivity and accuracy but there is a an obvious agenda behind it. When you do your due diligence this should be obvious.
And as to gambles... when an amateur buys stock its a usually a gamble, when a pro buys it; they don't gamble. They might take a calculated risk but they dont gamble. Watch 'the wolf of Wall Street' ; who do they sell the junk stock to? Is that honest business? No. But you can get rich with it.
And measurements? Really? Trust your ears? Yes, with experience or training. Measurements... that you even dare bring it up in an R2R thread.
Measurements mean nothing, mostly it's just marketing lies. And don't you contradict yourself here? Measurements vs trust your own ears?
So, you say sensible things, but your logic is off. Yes, sound quality depends on a slew of things. The marketing of the Musician dac comes across as shady to me and it doesn't give an honest answer to the questions about sound quality.