After 2 years of observing molts, I'll say ours don't go off their feed.
They get runny poop for about a week, take more naps and have a short fuse with other chickens for 1-2 weeks, and get pale/smaller combs for a few months. During the worst of the molt, it looks like they feel like we do with a fever: sore and achy.
Molts in our chickens have been lighter and more gradual in year 2, both for chickens in their 1st and 2nd molts. This past year, we changed their nutrition to 18-20% protein/minimum 0.4% methionine (up from 16-17% protein/0.3% methionine). Two Easter Eggers even laid regularly through most of their first molts. So, one hypothesis is that better nutrition resulted in a gentler molt.
I also worked this past year to lower stress by providing separate quarters for overzealous cockerels. Whether due to lowered stress, maturity, or long-term integrated pest management, the flock was also better at fending off our 2 biggest health issues in 2020: roundworms and northern fowl mites. Mites completely disappeared by spring 2021, and I haven't had to take poops to a vet for worm analysis in the past year. We're down to a prophylactic chemical deworming 3 times a year, with fresh garlic once a month in between, and mite powder in coop corners but not in direct contact with the birds themselves.
It's possible that lowered stress, parasite pressure, and chemical treatments may have helped reduce their molt severity as well.
Again, we're just 2 years in. In year 3, they may have severe molts, and I'll hypothesize it's all about the weather or the solar flares and moon cycles instead
