I wonder if the person you contacted got him to feed t he little guy nectar as well. Maybe, since he's growing feathers back. Something to take in mind, many times people think they are "spoiling" their animals by giving them what they themselves like..oreo cookies and tv awesome! Especially so if they get them from someone who didn't know or care either.
If the guy really likes the little bird, perhaps education is the best thing. My husband, I pretty much have to say junk food is poison to keep him from giving it out to all the critters. The only ones he's allowed to share his junky snacks with is the rats and I have been training him that nothing larger than their head, and no more than a few times a week. otherwise if you want to give them a huge treat...give them a piece of broccoli, they love it just it was candy.
Hoping for a success with this little guy and his owner too.