Seems pretty clear to me that a quantization of mass (say at the Planck
scale) would have to be accompanied by a fundamental discreteness in
space-time (also at the Planck scale --> 10^-33 cm and 10^-43 sec.).
The quantization of mass is then at almost macroscopic size and one
would probably have to view that mass as the mass of a free quark. The
extremely small mass of the proton then being due to all the mass being
radiated away in the formation of the proton from quarks. No wonder you
can't get the quark out in an accelerator. The Planck energy is 10^19
GEV. If all that were true, then potential and kinetic energies would
also be quantized.
J. Epstein