E, yes I have seen someone killed from a knife fight. Watch the instructional film, "Surviving edged weapons". It explains everything including the 21 foot margin of safety.
Watching the video...
Couple things...most of these interviewee's are obviously coached, and the interviews are cut heavily only showing particular parts of the interviews. The entire thing is alarmist... Red flag...but anyway, I never said edged weapons weren't dangerous or shouldn't be taken seriously. I'm saying that juts because you're within 21 feet of me with a knife, doesn't mean you're going to win the fight or even that you're going to have the upper hand.
Just like some guys think guns are the end all of a fight, some guys think all I gotta do is get within 21 feet and I'm good. Fights are very fluid and shit happens very fast. If I were only allowed to carry a knife, I would, however, i'm going to choose to carry the object that's going to give me the best chance at neutralizing the threat quickly and without requiring being within arms reach of the guy.