[mikeash]

Something as simple as moving the insertion point in response to an arrow key requires a big table of code point attributes and changes with every new version of Unicode. Seemingly simple questions like "how long is this string?" or "are these two strings equal?" have multiple answers and often the answer you need requires those big version-dependent tables.

I think Unicode is about as simple as it can possibly be given the complexity of human language, but that doesn't make it simple.