What the Heart Knows and the Ethics of Killing in Dishonored

PC Games N has an editorial on the ethics of killing in Dishonored, in light of the constant commentary of the heart. Here's a snippet:
It occurred to me that this is why Corvo must remain a silent protagonist, why we don't get much insight to his thoughts or feelings. His decisions are not like a Commander Shepard's, who is called time and again to the galactic stage to render another Solomon-like judgment on the fate of races. Corvo must instead make hundreds of small decisions that will have no visible impact on the world and which will never be known by the world at large. Does Corvo spare the brutal bully but quietly slaughter the serial killer? Does he simply harden his heart at everything that surrounds him and focus on the mission? Now that he has the capacity to read people's pasts and futures, doesn't he have some moral culpability for everything that will follow?

Fittingly enough, it is impossible to keep one's hands clean in Dishonored. Even mercy and restraint can become tools for a greater evil, if you simply pay attention. I spared two foppish aristocrats from assassination, only to discover I'd consigned them to a lifetime in a hell that would make Stalin's gulags look like a Siberian vacation. I killed one victim because, while she had to be removed from the board if I was to bring down the Lord Regent, the (nonlethal) option sounded like it made Corvo an accomplice to rape.

What do you say to something like that? How could Arkane write lines for Corvo that could reflect the inconsistent, confused morality I staked out for myself in my journey through Dunwall? In the final stages of the game, when my enemies were falling like leaves on a silent breeze, I'd come to a point where there were scarcely any lines left to cross. My Corvo began as a pragmatic professional and ended as a zealous crusader, an arc that took place entirely in my own head.