And thus the "as much as possible" caveat I added in.
According to Pros, if I kill an evil target (killing the troll), I have done a good act even if I didn't mean to. But, apparently, killing a good target is not a conversely evil act if I didn't mean to.
I have stated this a number of times, but I will repeat it again. I don't consider the woodsman to have committed an incredibly evil act. As evil goes, it's pretty vanilla and more in the realm of tragic rather than terribly evil. But, if you start with the premise that killing children is evil, then, yes, the woodsman has done an evil act. He is repentant because he is a good aligned character and recognises his action for what it is.
The problem with alignment that I see most of the time is that people try to come from the position that intent is primary. That if I intended something good, or didn't intend any evil, that excuses my actions. I don't buy into that. Not when alignment in D&D is absolute. An evil act is evil regardless of who does it or why, according to D&D.
I also notice that Pros is still mulling over my 2 knights question. Perhaps we could get his view on it?
/edit - A further thought occurs to me.
I just recently saw Pirates of the Carribean Dead Man's Chest. Good movie and not a bad one for giving illustrations for D&D alignment. Take the last (ish) scene where Captain Jack has returned to the Black Pearl to stand with his comrades against the Kraken only to be shackled to the ship by Elizabeth and left to be eaten by the Kraken.
Now, Jack's return is a pretty solidly good act. Coming back to help those in need at great personal risk is generally agreed to be a good act. However, if we let intent come into the picture, we come up with two versions. One, Jack's return heralds a reformation of the character and a rise to goodness through a selfless act. The other says that Jack came back to get into the pants of a woman betrothed to his friend and that selflessness had very little to do with it.
We could go either way in our interpretations. That's not the point. The point is, by allowing intention to cloud the issue, we can take the exact same act and paint it as either good or evil (or at least certainly not good). And, depending on which interpretation you follow, you cannot really reconcile the differences.
However, if we simply ignore intent, then the act is selfless and good. Elizabeth's action is evil, despite the fact that she was doing it to save everyone else. Her intentions are good - save as many as we can - but her action is pretty squarely evil. Her reaction to her action is in keeping with a good aligned character.