Sometimes, in duels, you cant click that box fast enough if you killl them in two hits....(one hit for unconsciousness) Sometimes, if you kill them in two hits or whatever...you click for the box to go away. And, just as you click it.....they are completely dead, therefor you accidently kill them twice.
This is definately a problem when you are not trying to duel someone, but just trying to duel.
Im not sure if this would work out, but it would definately be good if it would work.