Squatter toys with us,
HI.
Seriously though, our Man of Old English Letters reminds us of an important fact about this character. He was conceived in a different story culture. Like many an 'immigrant', Tom is not well integrated into the community or cosmology of this story. Having Gandalf refer to Tom at the end of the story represents a heroic attempt to integrate him, but one which remains I think somewhat mechanical. It is all well and good to call Tom an enigma, but by and large I think this kind of defense remains more a justification than a true explanation.
On the other hand, does the problem or enigma lie only with Tom? I find it very interesting how often people have difficulty understanding or accepting Tom, yet very few seem to ask who or what Goldberry is.
Do readers have an easier time accepting a female mythic earth character than a male one? Or is it that Frodo's infatuation with Goldberry provides an adequate and understandable explanation of her function? (Why is it that she can control rain, but not snow, for instance?)