Ted - that looks like a fairly major loss of edge definition - which is quite likely from the multiple scan registration issues discussed upthread. Colour noise is not difficult to clean up - however it looks like your multiple scans have been severely noise reduced by the methods of blending & alignment to the point that it's taken the edge off definition

Pere - unless you can point to exactly where Silverfast is altering the motor speeds in multiple exposure or increasing the output of the backlight, it's creating multiple exposures by manipulating the gain of the sensor - if it could boost the backlight or lengthen the actual exposure, the hardware dmax would be higher - and Silverfast explicitly does not make this claim.