Excellent post.Back to serious talk. Feathers do make more noise and esp the faster they are shot, at least in my experience. That said, I do not think it makes a lick of difference in relation to deer reaction, again based on my experiences. I have seen deer clearly react to the bow, I have seen deer seemingly react to the sound of the arrow on a little longer shots. I think it really boils down to the individual animal and I really cant put a finger on why they react the way they do. My experience last year is a perfect example. Opening weekend I had three does come into to a persimmon and when the shot broke, the deer I was shooting at went full blown matrix like a cracked out texas deer. This was on completely unpressured private ground too. Last shot of the season was at another doe on a food plot, late season hunting from a blind. Wind was swirly and she came in from the down wind side, bad skittish, head bobbing the blind, bounded off twice 20-30 yards and came back. When she got broadside I took the shot fully expecting her to drop hard. She was locked up like she just stared at Medusa and didnt move at all. Instead of holding lower third like normal I shot for just under her chest and that is right where the arrow harmlessly went. I guess my point is 2 fold, dont try to second guess what the deer is gong to do because there is seemingly no rhyme or reason for how significantly or not they will react to the shot or the arrow. I think our best bet is to set our gear up for as optimal of a tune as we can get and shoot for a lower third exit in the front half of the chest.
That general concept could apply to a lot of aspects of hunting like odor and wind.
Deer are individuals and each and every encounter is an entirely new deal. Do the best you can and don't make assumptions or take anything for granted.