What an amazing post! I really learned many things from it. Note that some dark chocolate may contain less sugar (IMO, there is in general too much sugar in chocolate). On these lines, I was wondering whether you would know how the amount of sugar influences the tempering process?
It changes the quality as one would expect. With an increase in sucrose, the viscosity and resistivity of the mixture augment (although the effect is relatively small, not something most chocolatiers concern themselves with) thus the nucleation is slower. In concentrations of sugar below 35%W/W monodispersion increases and above that it decreases. The effect can be seen in the size of the fat droplets that form. Without milk or sugar, the crystallization would be slightly more heterogeneous and type V crystals would take less time to form. The problem is bitterness.
I don't see bitterness as a problem for chocolate, personally (I like the 99% dark chocolate made by one of the famous brand. Very better, but so wonderful). But tastes are subjective, of course.
Thanks for answering!