I'm against it, Discord being reformed is as silly as the Joker being reformed and I feel if the writers continue on a path of him being 'good' I feel it would be a loss to the show. We need more manipulative villains like Discord yet they are sadly not as common, and was because of the cruelty and selfishness of his actions towards others that I enjoyed him so much.
You don't need to kill or physically harm someone to be evil, and I felt Discord showed this very well in Return of Harmony. As of right now, unless I'm proven otherwise, I'm treating this as him faking his reform. Though it is possible that he may have gained a fondness for Fluttershy thus making her his "Morality Pet" (TV Tropes) but even then I don't believe it will last.
I dont really like it because Discord was like the only Vilan and i though the final episode for season three was going to be like the Mane Six and the CutieMark Crusaders would turn him back to stone! me no likey.