Well, it seems like I failed in my attempt not to derail things. Sorry @johncarlosbaez!
@johncarlosbaez Ironically, being the cause of the distraction, I thought it was a quite interesting question. What you said certainly sounds plausible, asymmetry can often arise in an open quantum system via decoherence of a symmetric superposition. It seems to me that I've heard people refer to the inhomogeneities in the CMBR being the signature of pre-inflationary quantum fluctuations, but I don't think I've ever heard any discussion that talked very rigorously about how they arise, as far as the quantum state and decoherence mechanism.
On the latter point, all the decoherence would require is that the stress energy tensor coarse grained over astronomical distance scales be couple to other degrees of freedom.
@internic - thanks. I'm getting fascinated by this question; I will ask some people about it!
@internic - that's okay. People here clearly find it more fun to talk about interpretations of quantum mechanics than figure out whether an initially perfectly homogeneous state is compatible with the inhomogeneities we find in our Universe today. And maybe that's no surprise: I'm having a lot of trouble finding any discussion of the latter question. The closest I can get is people talking about the power spectrum of inhomogeneities in the inflationary era, whether it's Gaussian, etc.