I agree with you completely about the "split personality" scenes in POTC 3, and had dark suspicions that Depp insisted on them to get more time playing the character. :-)

And you're also right that it's a mistake to think too hard about the movie. As we were driving back from POTC 3, esrblog started trying to figure out what real-world time period best approximated the period of the movies. Fortunately, it only took me a few minutes to convince him that they were so historically inconsistent that it's much better *not* to try mapping in real history, but to enjoy it for the made-up world that it is.