I'm reading this thread and so far have gotten to your post, about halfway through the thread. From what little I've read of Faynman who is not a layperson, by any means, and what some knowledgeable folks here have said, there is much which remains mysterious, if you will, about QM and in one of Feynman's papers he simply said something to the effect that certain aspects of QM didn't make sense.
Yes, Feynman did spend a good deal of time pointing out the mysteriousness of QM... to layman and non-specialist audiences. But don't for a second think that Feynman was confused. You have to appreciate the difference between the workings of QM and the interpretation of QM. The Copenhagen Interpretation is precisely that... an interpretation. It does not in any way affect the workings of QM. From every experiment carried out over the past 100 years, those workings are fixed in stone.
Most interpretations, to some extent, try to explain QM in terms of classical concepts. This is always a lost cause because QM contains concepts that have no simple classical analogues. But some interpretations lead to new ways of performing the calculations. One of Feynman's greatest achievements was the path-integral or sum-over-histories approach to QM, which is mathematically equivalent to Schrodinger wave mechanics or Heisenberg matrix mechanics, but has a very different interpretation.
What I have been trying to say is this: it doesn't matter what interpretation is used, no extra mechanisms are discovered. The underlying mathematics fixed long ago the possibilities of QM.
That is not to say that there is nothing new to be discovered! But it is not in the "mysteries" of QM, but in the search for the TOE which means the ensemble of "the problem of time", "quantum gravity", "grand unification", "quantum mechanics", "emergence", etc.
If you think QM is mysterious, just try putting your mind around that lot. That was my job...
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