Jim,
I really haven't researched this extensively, but as was stated earlier in this thread, potassium sorbate is birth control for yeast. It does not inhibit their fermentation of sugar into alcohol. In addition, yeast reproduction is also inhibited by high levels of sulfite, as O2 is necessary for reproduction, albeit in very small quantities, and sulfite binds O2 and removes it from solution.
"Jack Keller notes that he has seen dead yeastsediment drop out after as much time astwo months after stabilization"
I take this with a grain of salt. Unless he has examined the sediment under a high power microscope, there is no way to determine if this is or was active yeast cells or just micro solids that coagulated into macro solids and settled. The human eye can only detect particles so small. What looks clear may not be. It takes very sophisticated equipment to determine the actual turbidity of an almost clear liquid. These instruments, which cost thousands of dollars, are used by municipal utilities using surface (river and lake) water for their potable water source to evaluate the performance of their clarification procedures.
For true scientific information on the chemistry and biochemistry of potassium sorbate the first place I would look is the Univ. of CA Davis. They are at the center of winemaking research.