: The Didact's personality from Halo
: 4 makes more sense now (but I still feel that he could've been
: characterized more strongly in Halo 4, as his personality still barely
: reflected that of the Ur-Didact we see at the end of Silentium)

It appears that both Ur-Didact and Faber had contact with Gravemind/Primordial. The Didact of Halo 4 may have been angry at his imprisonment. The question is what was his real plan? Was he going to make all humans into nonorganic warriors? Why did the Gravemind/Primordial let him and Faber go free. I feel it's the beginning of a much larger game, a chess match over eons.

: Questions and thoughts to ponder: *If the Precursors chose Humanity for the
: Mantle, and went so far as to protect us for this reason AND to get back
: at the Forerunners, why attempt to destroy us in the main trilogy? Maybe
: they weren't? Maybe they were only trying to defend themselves? Do
: remember that the Halo 1 flood did not have the benefit of being educated.
: And the Gravemind did pass over Earth; maybe this is one of those reasons?

It appears the Precursors did favor the Humans for a time, but their own logic has become evil and twisted. It seems they favor a complete control/infect solution now.

: *Bornsteller survives activation? Damn, twisty. So what does his future hold?
: Do any of his future (now past) actions have any unforseen effects on
: future events?

: *Also, what of the new Lifeshaper, Chant-to-Green? What other actions might
: she take in her remaining lifespan? Is this the version of the Librarian
: the fragment of 343 seeks?

Perhaps Bornstellar has his own Lifeshaper. I think they are left as prime candidates to rebuild the Forerunner.

: *And how long will that truly be? Do the Forerunners attempt to continue
: their existence? Where? And for how long?

Far enough away as to not interfere.

: *And last but not least...the Didact's final protector, Endurance-of-Will?
: Does she become a Promethian machine even though the Didact no longer
: stands to force it? What comes of her?

Perhaps she rescues him after he falls back through the portal. We will have to wait and see.