Just realizing now that the italicized chapters are those of author intrusion; Martel perhaps, as narrator, rightly in the future, looking back at his first meetings with the character, Pi.
Maybe close reading is not close enough, or too close to see.
Martel's use of this in what I am now considering to be a work of fiction, despite the opening Author's Notes, is likely to keep the reader in close proximity to the story–by keeping him close to the storyteller. This is effective (I'm sure, though I'd missed the whole point up till now) in perhaps building the dramatic effect of the story by ensuring that there is a future for the character, and tying together the boy of the story to the man of the author's chapters.
The Lost Children: A Charity Anthology