I have heard MQA and it isn't easy to tell the difference but over a period of time it sounds more relaxed.
Having said that the mechanism has
been taken apart at Computer Audiophile.
They basically use minimum phase resampling filters which among other things end up rolling off the HF creating the sound signature.
All this is easily done in software nowadays with the SOX engine or HQPlayer etc so the whole circus of creating a new format, hard wiring the codecs into the ADC and then the DACs is laughable. Their whole "folding" terminology and claims of fixing time coherence etc is a joke. What is a down right scam is the elaborate process they have cooked up for manufacturers to qualify and then the penalties for not complying etc. The big media companies are more than willing accomplices as they look for new ways to squeeze revenue out of their customers.
So now not only do you have to buy the new MQA version of Miles Davis "Kind of Blue" (in addition to the RBCD, Hires and DSD versions you already have) but you also have to purchase a new MQA DAC to get the "full benefit". The studios on their part had to send their master files to MQA for processing etc.
In my honest opinion MQA is a scam. Whatever they claim they are doing is pure hogwash.
They are definitely not "Master Quality Authentication"
MQA is a "marketing solution" for a non existent problem.