A discussion instead of simple flaming? I am quite impressed, Gentlemen.
I was wrong. The DS guards did not produce sparks:
DS guard
And I was maybe wrong with the AT-ST driver, as well. (However, they did not wear armour like Veers on Hoth, it seems they have only a vest:
AT-ST pilot) The burned spot can be traced back to the shot. It is true. However, it can be traced even further back:
Burned spot.
Leia did not react immediately. It is true. She started to react on the 8th frame. The AT-ST pilot I mentioned started to react on the 5th, the imperial, who was hit by a box (thrown by Han) started to react 7 frames prior to hit. So, we are talking about approximately 1/3 of a second as problematic (and app. 0.1 second difference between that and a similar ocassion), and that problem remains with the bunker was hit theory. (Unless, you state that she should have reacted to a blast that burnt through her uniform, but should not have reacted to a localised heat effect that did the same.)
Greedo produced sparks. At least, it is unquestionable. If you want to explain that with "armour worn under the clothes" I have to ask, why do you throw away canon evidences, when this "technology" could explain Leia's case just as well?