I disagree about the sparring partner thing. a sparring partner should push you to your limits and you should be pushing back. ive been clocked hard before usually by shots i didnt see coming, although ive only been dropped once in training by a headshot (well and a broken nose but i didnt go down so it doesnt count :p) I find the idea of "i could have hit you but didnt" is a **** way of training because you have to leave it up to the guy you didnt hit to decide. i would rather not give people that option. if someone has holes in their game you need to fill those holes preferably with a fist (or your wang if you do BJJ)
i mean of course, people who come in swinging for the trees and looking for a KO in sparring are frowned upon. these kind of people dont tend to last because then for their hard work they get to spar with someone like Chapman which is a bit of an ego killer.