I think I can see most all sides of the technical arguments. I think part of the underlying problem is that MQA goes so far out on a limb by using claimed psychoacoustic advantages, including many that are not widely accepted, if they indeed ever will be.
As much as Stuart, et al, have published justifying their technical approach and alluded to psychoacoustics, they have not concretely proven the advantage to the listener. And, skeptics who do not accept those psychoacoustic assumptions and lean heavily on traditional theory, give MQA a hard time and throw rocks, to put it mildly. Of course, other counterproductive and often nasty speculations and red herrings - DRM, Meridian/MQA ownership/profitability/financing, that Stuart is a liar and a fraud, etc., etc. - have also been spawned by those who do not wish to see the technical status quo upset in any way.
If it is fundamentally about psychoacoustics, then only carefully controlled listening tests can truly demonstrate any superiority of MQA. So, I agree with others in this thread on that. I think Archimago (I am usually a fan of his) has offered a nice try, but one that might be open to serious questions as to its rigor. I say that in the middle of reading Toole's excellent Sound Reproduction -3rd Edition, in which he clearly defines how to go about conducting such rigorous psychoacoustic testing based on listener preferences and correlating those to measured, technical observations, brilliantly and convincingly I might add. But, speakers in rooms are his sole interest.
We do not have such tests. MQA could not themselves conduct them. They would be dismissed as tainted. So, who might conduct them and when? I note that DAC-maker Berkeley claims to have done this as part of their due diligence before accepting MQA, but it is unpublished. Maybe no one ever will publish it, and it will be left for audiophiles in the marketplace, subject to the usual chaos and lack of scientific discipline.
I find one thought by Ken most interesting: the notion of a true end to end, analog to analog recording/playback chain using MQA directly in the a-d and throughout the chain, as opposed to MQA being used to post process the result of traditional a-d later in the chain. MQA has not openly described this possibility. But, I would love to hear the results alongside a conventional hi rez chain, difficult though this might be with today's studio equipment infrastructure.