Endgame. Spoiler within. You are warned.

Yes

It would make sense [spoiler]because in the Forerunner series of novels, Forerunners go through several stages, I think they were called mutations, where they change physically and psychologically, and this is how they advance themselves. They can mutate themselves, or they can mutate with someone, which is what happened when the Librarian changed the Chief. When the Didact mutated with another Forerunner named Bornstellar, the Didact himself didn't change, but Bornstellar changed to resemble a cross between himself and the Didact, and Bornstellar had all the memories of the Didact. He also retained the Didact's personality, effectively implanting a copy of the Didact in Bornstellar's mind.[/spoiler]