Sounds plausible, collisions with high energy particles emitted by the sun could certainly brake down ice/dust crystals. I would not argue against the possibility.
now if you add up the tonnage that will be in path of earth as it slides through both ISON’s exit and entrance path then well....
That’s a lot of small debris..how will out atmosphere react to it and will it have effects similar to what a volcanic dry fog?
That is my take.