
Now I think that this discussion brought about one important point (and I hope I am not wrong about that, I haven't played for some time). Misdeeds = SP (e.g. causing pain for fun, unnecessarily, or excessively). What is the level here is difficult to say and there should be harmony here between the LM and players.
But even being just a part of an act that is just in itself (like killing someone, or being "just a soldier" in a conflict like that which happened in Alqualonde) might require corruption check.
Why? It describes like the evil that is present in the world affects everyone and how on must set his / her determination against it to prevail. Being in war influences you - some for better (they understand more about world and how precious every life is - Faramir), some for worse (trying to win their war at all costs - Boromir or say Artyom in the end of Metro 2033 (the game)). I think that laying a corruption test upon a player whose character just killed for the first time, or whose character had to kill or harm someone they loved, brings about the complexity of moral choices far better then simply awarding SP - or doing nothing at all. I think it can create very strong situation in the game on emotional level.