Also there is an interview at TheQandA podcast. Pretty much the same territory covered as the IO9 dialogue from yesterday.
Seems he did think about most of this stuff, my favourite idea from IO9 thread was (SPOILER) Kid Blue was Abe's younger self.

Also I was STUNNED how good that 5year old kid was!

And on a VFX side, those keyed shots in the paddock at the end were amazing, so clean and detailed.

Down side, the hover bikes sucked bad. It's sucha  shame, whenever they appeared the physical and digital effects were just so naff. Oh well.

I really enjoyed this movie.  Soooo much better than Inception.  When I was discussing this film with a friend, I voiced only two gripes with the movie.  1.  I wish we would have had more time developing the relationship between Bruce and his wife.  Her death is such a huge part of Bruce's motivation, that she needed to be more of a part of the story.  2. We needed to see Bruce be affected by what he was about to do to the kid and his "mother" towards the end as JGL's character developed a bond with both of them.  I just felt it would have made the finale that much stronger if they had done that.

He talks about that in the commentary. They deliberately assembled the murdering-kid scene such that it would turn the audience on Willis a bit.

There's absolutely no rule against it, and killing kids isn't even remotely new. Carpenter did it in Assault on Precinct 13 over 30 years ago, and there's probably way older examples. It is true that especially nowadays you mostly see it in just trashy grindhouse movies like Planet Terror or Hobo With a Shotgun, but it's not really for MPAA reasons. It's just one of those things film-makers don't want to do unless there's a good reason for it, which makes sense to me.

I don't think it's necessarily conservative christian morals that drive the concept, just the filmmakers making a decision on their own.

Or even beyond that, adults have at least had a chance to live through a certain part of their lives. The younger a victim is, the more troubling it gets because of how much they are losing, whereas killing a 100 year-old feels inherently like a lesser tragedy.

Is it more or less tragic to murder an adult for what they have done or a child for what it hasn't but will or might do? If adults are inherently less innocent and all children grow up to be adults and thus lose their innocence along the way, then isn't it ultimately the same result, and thus more of an issue of timing?

To my mind, the idea of childhood innocence is that they've had less opportunities to do bad and have a lower quota, not that they haven't done bad period. So it's a bit of crock, like 'sanctity of life'. Equally, depending on the age of the child, they're quite capable of knowing what they're doing and the consequences, the difference is that they are to a certain extent sociopathic; they haven't yet been temperered by their social environment to conform and obey social rules. Kids love doing naughty things and do so out of curiosity, boredom or just because they can. In adulthood we learn to only do such if we can get away with it, as we are more fearful of the ramifications of being caught (embarassment, exclusion, financial penalty), kids aren't as bothered.

I said "lesser" tragedy, doesn't mean it's not a tragedy.

If you want to argue that you'd save an old-man instead of a child given the binary choice, be my guest.

And I don't even like kids.

Son of Doty is not to be messed with