Remember the anti-drug commercial that shows you an egg and says "This is your brain," and when the egg cracks open into a hot skillet, the voiceover says "This is your brain on drugs. Any questions?"
That's the mental image that kept coming to mind as I read through Unknown Screenwriter's posts about character depth. It was as if he held up an egg and said, "This is your character," and then dropped it into a scorching pan of scrutiny and said, "This is the depth of your character. Any questions?"
Oh yeah. I had questions. My yolk splattered everywhere.
Certainly, there is truth in the notion that writers can over-think individual aspects of their craft to the degree that spontaneity and creativity suffers, but character development is critical and SHOULD be overthought. Read these posts and remember the egg:
Depth Charging Your Characters
Depth Charging Your Characters Part 2
Depth Charging Clarifications