Not in the PC version at least
probably a networking thing
E: Actually, I've noticed times where people will be shooting me and I'll zoom out, though I've taken no damage. Yet, it's possible to take damage and not zoom out. I'm willing to bet if you shoot someone straight on (not leading) in Halo PC while they're zoomed in, it'll make them zoom out.
Also, collision on the Reach models is no bigger than it was in Halo 1. If anything it's the auto aim. Compare the collision when betraying. No easier to betray someone in reach than it is in Halo 1.
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