From a user point of view i would expect preview Color showing current Layer only, if the commands result creates new geometry - not modifies it.
Technically this might be related to some stuff related to Rhino.Input.Custom.GetBaseClass.GetPoint or similar.
some examples:
(preview = current layer, result = input layer)
_insertPoint
the SubD is on black default layer, but the snapped Point is red
_insertEdge
same as insertpoint
(reversed: preview = black, result = current)
_point _between
this is the reverse - preview color is black, newe geometry is on layer01 (red)
resulting in
… i think a consistent preview color (white, black, current layer, output layer) is an important criteria for the next round of “polishments” …
thanks for having a look - kind regards, tom