I understand in the LHC where particles are moving close to the speed of light. Relativistic effects are very obvious and QFT is required. But is it not in normal atom even how excited states of the electron emit a photon need QFT treatment? So not just relativistic effects?Neither one involves any relativistic effects, so no.
Anyway. I finished Lubos Motl many articles linked in the OP. So the bottom line is :
"Instead of specifying observables (linear operators on the Hilbert space) and calculating their eigenvalues and their probabilities of individual eigenvalues given some knowledge about the state, they keep on asking whether some "cloud here" affects another "cloud there" or whether it "collapses", assuming that the clouds objectively exist in the classical sense. That's not a good starting point to understand the essence of modern physics."
Lubos is very authorative. Right now. I wonder how large in percentage of physicists hold that view. I was so exposed to Zurek, Demystifier, Neumaier etc. views over the years I tend to ignore Lubos views which may still be the majority?
To clarify your own article when you commented "But if we take that idea to its logical conclusion, it implies that QM must be an incomplete theory; there ought to be some more complete description of the system that fills in the gaps and allows us to do better than merely probabilistic predictions."
Let's take the double slit experiments. Lubos seemed to be emphasizing we must only focus on the output and not how the the one electron at a time version can interfere with itself. So does your "more complete description" just involved *trying* to figure out how the one electron behave when it is in between the emitter and detector or did you mean something else by "more complete description"?
And for the questions how it *interact* in Lubos or orthodox view, the answer is that it is emitted in the emitter and just appear in the detector. No interaction. Period"?