Jasper being that insane, instead of more like Marcus, Irina, or Bella, is a direct consequence of his personality, the nature of his and Alice's relationship, and the exact circumstances surrounding his particular situation, including particularly the experience he refers to when he says he felt Alice die.
Everyone reacts to their mate's death differently, and how said mate dies matters a lot. (For instance, Maggie would have had a unique reaction if she'd eaten Gianna when they met, versus if Gianna had died trying to carry Elspeth to term. And if Maggie had finished crushing Gianna when Gianna was turning, that'd be a whole nother can of worms yet.)
In the vein of the Harry Potter and the Methods of Rationality discussion threads this is the place to discuss anything relating to Alicorn's Twilight fanfic Luminosity. The fanfic is also archived on Alicorn's own website <strike>(warning: white text on black background)</strike>.
Previous discussion is hidden so deeply within the first Methods of Rationality thread that it's difficult to find even if you already know it exists.
Similar to how Eliezer's fanfic popularizes material from his sequences Alicorn is using the insights from her Luminosity sequence.
Spoilers for the fanfic itself as well as the original novels need and should not be hidden, but spoiler protection still applies for any other works of fiction, except for Harry Potter and the Methods of Rationality chapters more than a week old so we can freely discuss similarities and differences.
EDIT: Post-ginormous-spoiler discussion should go to the second thread. (If you have any doubt on whether you have reached the spoiler in question you have not.)