First, I feel the need to apologize for my first insult-heavy comment
Second... I can't STAND that theory because it's objectively terrible. Discord is like the Joker from Dark Night. The terror and humor he inspires is magnified by the fact that he has no good reason to be evil other than "it's fun"
But when you give him a "spurned lover" backstory, it replaces all of that with sympathy. He's not scary or funny anymore, just a sob-story. And that's bad for the overall story