You're not getting the point. The arrow was clearly embedded in the armor -- it didn't bounce off, or fall out after only a little penetration. It is IN the armor. If it manages to achieve even partial penetration, then you could expect a modern bullet, which is a MUCH better penetrator, to achieve complete penetration. And the fact that he yells implies that the arrow did some harm to him, as well.
The scout trooper has a backpack, and the arrow is not deep enough for it to have punched through the armor and hit the man inside. That he yells implies nothing other than he yelled. Could have been from the sheer surprise of feeling the hit.
It's more likely that the arrow hit the unarmored neck area. I mean, notice how the OTHER 2 scout troopers aren't even injured, and how none of the Ewoks use arrows after that initial volley. Probalby because they realized they were useless.
As for the cracked shoulder-pad: it could have occurred anywhere? Alright, but from what? There aren't many threats in the area other than Ewoks and well... hills. So either he fell down the hill and it cracked or an Ewok managed to crack it. Not much room for interpretation there, and either way it speaks volumes about the weakness of the armor. The fact that it could be a simple defect doesn't encourage much confidence in the stuff, either.
Alright. So if it's from the hills or arrows, point out all the other cracks in the stormtroopers.
Oh wait, there aren't any. As I said, that crack could have occured anywhere, in a previous campaign, in an accident with some machinery, etc. Darkstar never proved that it occured during that fall down that hill. And sometimes defects happen. The fact that it's the only crack in any stormtrooper armor ever seen in the movies DOES speak about confidence in their abilities to make armor.
BTW: the crack doesn't even impair the armor at all. It's not a giant gaping defect, it's a crack.
Err, and? I suppose you think you're clever. Not really. I was well aware of that article and the details of what it says years ago. Hell, I even acknowledged it in previous posts. Either way, that's a wiki, and I've yet to have seen specific instances from canon to back its info up. My source is the movie itself.
Your source is the movie, yes, but your argument is taking a crack seen in the movie and a scout trooper being hit, and then saying "The crack MUST have been caused during that battle!" and "The scout trooper MUST have been killed!" without offering sufficient reason as to why.