Mookie, thanks for contributing. I tried to explain energy transferrence and kinetic linking earlier in the thread. Good TKD instructors definitely train to kick 'through' a target. As to rechambering (pulling back) a solid kick to increase the power.... I'll have to look into that. I don't quickly see the value from a physics perspective. The main reason we train people to rechamber their kicks is for a couple reasons.
1.) To avoid having the limb captured and/or losing your balance. No point in landing a solid kick only to be taken down or falling down.
2.) Loading up for another round (Pretty much exclusive for sparring and Van Damme movies) I've scored a lot of points with double/triple kicks in sparring tournaments but that is something pretty foolish to try in a fight.
If you can find more reasoning for rechambering please contribute them. If I come up with some more ideas I'll share them as well.