Don't forget that I mentioned that the impact causes damage, not that an injury is any kind of impact. (you do raise a good point about twists of joints not and impact, but there is usually some kind of force making the knee, wrist, ankle turn). All impacts obviously don't cause damage to the body. I've taken probably a few thousand rolls by now and I haven't been "damaged" by all of them, just those really painful ones in the beginning where your shoulder hurts so bad you don't want to do another roll. I have also been accidently hit in the face and had no resulting bruise or damage -- that's not an injury. If I had a bruise/ black eye, then it's an injury. I get grabbed all the time in class, but when my stronger partners really bear down on my wrists they sometimes leave bruises. If no bruise, then no injury.
My point is that just because something is relatively minor doesn't discount that fact that it is an injury. Jun didn't ask about bad injuries, injuries that kept us off the mat, injuries that disabled us seriously. He just asked if we were injured. I'd assume that most people have common sense to know what an injury is and we wouldn't have to play semantics games to answer the poll. (Although it does make it a little more fun in discussing the poll.
I also have the suspicion that some martial arts folks don't want to admit that minor injuries are injuries because some martial artists like to be stoic and "work through" an injury or even train when they have a cold.
I assure you, I'm smart enough to know the difference between and injury and no injury and that my vote was appropriate. I'm sure everyone else is smart enough, too.