My kdr reads about 700:100. Very bad. But that's because back when I had crappy gear I used to go out for a match or two just for the achievs. Imo, kill farming means chasing a person and killing him/her again, and again, and yet again. That always used to happen to me. Finally I geared up and earned that 100 while gaining maybe 20 deaths. So at least imo, kill farming is when you farm kills of an enemy.