The only parts I weren't already aware of were the conversion of Bornstellar to the Iso-Didact and the Librarian's "seeding" of Earth. Or rather, her "seeding" I interpreted as seeding with the precursors of modern humanity. If that guy's interpretation is true, 343i were absolutely right to initiate a second trilogy. The story- Chief's story, anyway- isn't complete until he comes to understand himself and his place in the galaxy.
It would be nice, though, if people trying to put together a serious argument wouldn't pronounce "sentient" as "sentinent", "librarian" as "liberian", etc. It was a little hard to get though with all the mispronunciations scattered around.
I think everyone's been confused by Guilty Spark's monologue there though. It was never addressed... Maybe Bungie didn't see the need to complicate matters and just left it untouched in the bible that presumably 343i now have? Maybe 343i found it and decided it could be used as a jumping off point for their own "fanfic". I dunno. It would be fascinating to know if it was truly intended from the get go though. There must be a reason for that monologue... For the purposes, any other speech could have been used, but they went with that.
Maybe this part of the story was Bungie's original intent with the MC trilogy but the story led off somewhere else in the end? Or they felt they couldn't really do the Forerunners justice without having a reason to properly introduce them first- the Ark, etc. So it became the Battle of Earth instead.
Having not played Halo 4 I'm a little in the dark, but it's a cogent reasoning. The question is, I suppose, if true, what aspect of Chief is Forerunner, and how does it affect him? He seems to strongly retain his humanity and be generally ambivalent toward Guilty Spark. Perhaps it's simply the ability to deal with the Flood. Is it, somehow, the reason for his "luck"? Somehow the galaxy is responding to his "Forerunner-ness" without the aid of their megascale engineering devices? Sounds a bit handwavy.