I've done this. Nice to sneak up on that Merc and get him. I feel like the guy from "Apocalypse Now".
EDIT: Apocalypse Now: Pirate Version.
That mercenary was standing there. He was challenging me in a way. Half of me was afraid to approach him, the other half wanted to chop his head off and play soccer with it. I was free to go, but didn't. I took another look at him. He wasn't a fearsome soldier, he was a sick poet. He wanted to die like a soldier, though. To die standing up instead of curled in a fetal position when a pack of mastered pirates gang up on him. I made my choice. Oh jeez, nevermind, there seems to be a napalm strike closing in.