In the rules of Paladin, there's a chart for combat outcomes depending on whether someone is Active or Reactive. As I understand it, an Active Flesh attribute is utilized whenever you're the subject of a sentence ("I do this"), and Reactive is used whenever you're the object of a sentence ("This happens to me").
So, I can see that in a duel there might be an Active and Reactive participants (an attacker and the victim), or possibly even two Active participants (each one acting very vigorously). But how can there be two Reactive participants? What does that look like? Or am I misinterpreting the Active/Reactive dichotomy?
In combat, the use of Reactive attributes just reflects a more defensive and non-lethal combat style.
The aim is not to kill or injure the opponent, just to defeat him. Defense is also better, because in case of loss, the reactive player chooses how to distribute the damage. (see the combat table for more accurate details)
Does that help?