> What happens when, as most people assume, Arwen shows up to give him the sword in RotK? Why should Denethor/Faramir believe his lineage just because Elrond decided to send him the sword?

Why should Denethor/Faramir believe his lineage just because he's got the thing in the first place? I can probably lay my hands on any number of family heirlooms without being part of the family. The house of Isildur was thought extinct -- if that were true, would it be unlikely that some schmuck would run across the thing and carry it around with him? I think I'd be more likely, not less, to trust the word of a respected eyewitness to Isildur's line, although I agree that that isn't really enough to reinstate a line of kings after so long either. I see it as a flaw in the story either way; consequently, I'd vote for the more literary device for the book and the more cinematic device for the movie, exactly as things are.

It's an interesting point about Aragorn's character, though, masquerading as Strider while simultaneously clinging to the most important heirloom of his true family; still, the heart of Aragorn's inner conflict comes across in the movie, though subtlely, and does not suffer any more than complexities as this must in the transition to the screen.

Of course, to an extent this whole discussion is premature. One or both of us may change our tunes next year when we see how Aragorn's claim to the throne actually works out. Until then, neither one of us have any basis for critical judgment on the matter.