One thing I'd like to put in two cents more on:

This concept simply means that your character does what her role dictates.

This is something that, though seemingly simple, does trip a lot of people up. If you're a paladin, your role doesn't have to be about killing evil (there are a lot of different ways to approach that class.) However, if it does, I should see you out killing evil... or at least, trying your damnedest.

The phenomena that originally drove PK tracking was numerous characters that swore up and down they were the scourge of the mud and had butchered their enemies countless times... and hadn't. Ever.

Likewise, if your character doesn't believe in killing, his/her actions should reflect that, as well.

That principle applies to all roles, not simple those that are especially murderous or non-murderous. There's no greater player-RP joy for me as an administrator than a player who makes an atypical choice in a typical CF situation because it's what their character would do, even or especially when I can tell their instincts as a player tell them to do something else.