Correction.
I have on my own initiative knocked out a variety of NPCs and foes, not killed them. I have also allowed that as a course of action in some cases when the party members ask it.
I believe you will recall that it was me who babysat the knocked-out copper dragon - and would keep knocking it out if it woke up - while the rest of the party wandered off elsewhere.
That fire cult is the only Kill On Sight group I have in my RoE for a good and sufficient in-world reason, and a better in character one.
(The "I don't fight for sport" bit is a recent and emergent bit of character development).
You will also note that I could have killed that archer, but did not, preferring instead to talk him down, share my rye whiskey with him, and try to make an ally of him.