Aha! Something that I can add. I read an interview last week by Mr. Ledger who spoke specifically to this "aging" question. He was very deliberate in trying to age Ennis, not through physical attributes because age 19 to 39 would not offer much in the way of aging. Rather, Leger tries to age Ennis through his clinch-fisted voice. Ledger worked very carefully through the film to progressively change Ennis's voice so that as he sounds younger and more audible on BBM, presumably the audience can make out most of what he says. But as you move through the film, it becomes more and more difficult as his voice becomes less understandable. I forget which interview I saw on the web, but Ledger talked at length about working on the accent, voice inflection and gradual disintegration in his audibility. He paralleled the transformation in voice to Ennis's being more progressively closed and withdrawn over time. This continues to reinforce the significant and compelling "investment" Ledger delivered to this role...
That being said, this means everyone on this forum needs to go back to the theater (for the nth time) and now listen astutely for this change in Ennis's voice through the course of the film...not that I'm twisting anyone's arm to convince in going back. Just another thing to watch for....
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