The Chaos system isn't good and evil. Every action you take is bad (Mutilate a guy, put 2 into slavery, abduct another; these are the "non lethal" approaches).
You have a few small chances to be good, generally by rescuing innocents, but they only factor in as minor influences to the overall chaos.
Chaos is that grey area people keep talking about when arguing against the traditional binary good and evil games. Yes Dishonoured has a "good" and "bad" ending (well... good, bad and bittersweet), but the game doesn't strictly punish you for doing something bad.
In my first low chaos run, I focused on avoiding detection altogether, only incapacitating people who were obstructing my path or about to call an alarm. To avoid some alarms I even killed people, since the impact of an alarm can lead to higher chaos scenarios (guards on high alert makes it harder to sneak, even on high elevations).
In my second run I aimed to remain stealthy, but decided to kill all my marks (instead of non-lethal). When I got to one particular point towards the end of the game I was still on low chaos, despite being more liberal about killing (guards and thugs included). That only changed when I decided to rampage my way to the target... which was particularly satisfying since he looked as though he shat himself upon confronting him.
Corvos Motivations are pretty simple, though its up to the player to decide what's more important. Redemption or Revenge. This is probably the games Achilles heel... there is very little attachment between you, Corvo, and the world you're in.
Also... quick-loading because you were spotted? This game is all about consequences and dealing with them. The game doesn't go to a gameover screen upon detection for a reason you know.