Not so much 'debunked', but this article calls out Krakauer on a number of conclusions and omissions from his book (and the subsequent movie). To summarize: the poison/moldy seeds theory doesn't hold water, and McCandless probably just simply starved to death. McCandless had money and a map with him on his final trek, but the book and movie omit this. Also, one of the final self-portrait photographs might have a clue as to the "injury" alluded to in his final note: one sleeve of his shirt looks armless.