Excellent post, by the way, Exile. I enjoyed the explanation using the language metaphor. The premise you make explains why I always enjoyed trading kata and kata bunkai with other karate-ka particularly if they come from a different system than I do.
And thank you for your thought-provoking comments in your earlier post, dancingalone, that got me thinking about what follows from thinking of kata as a kind of code, subject to rules of combination and rule of interpretation!
I have to say, I find the aspect of kata training that involves deciphering the applications one of the most appealing things about the MAs... for the same reason that puzzles and logic problems are so addictive for so many people. The point you raise about the possibility that not all movements in a kata actually correspond to combat moves just raises the ante on the difficulty in the problem, in a way. In a sense, it's easy to solve a puzzle if you know that you have exactly the information you need to solve it, not one bit more or less. But if you're given extra information that doesn't play a part in the solution... but you don't know that that's the case... it makes the puzzle way trickier, eh? Having moves in kata that may not represent parts of the combat scenariobut you don't know for sure that that's the case, and you don't necessarily know in advance which moves those arethat makes it way, way more challenging...