Everyone says its good for a moulter. One of my chickens had her feathers pulled bad soo...
The reason that it can be suggested for molting chickens is that chicken feathers are made out of protein (keratin). Most commercial (at least most of the popular common ones) chicken feeds contain only plant protein (soy) and it is not as readily available to a chicken's body to use to rebuild feathers.
Hence, cat food is suggested as a source of
extra protein.
However, there is a lot of junk cat food out there, and even in cat food vegetable protein is used as a filler oftentimes and to "increase" the protein ratio for cats.
If you read the label and ingredients, you can get a good feel for if the protein percentage is higher than your current chicken feed. If not, skip the cat food. Otherwise it's just junk and doesn't even give more protein than your current chicken feed!
If the protein source (look in the ingredients) is junk, skip the cat food.
Some higher end cat foods have good protein sources, but at this point it'd probably be cheaper to buy a good can of tuna...
Small amounts of higher quality meat (fish, beef, cooked poultry, game meats) or insects (such as mealworms) are going to be much more beneficial than cheap commercial cat foods, and you will get more bang for your buck in terms of effect on feather growth.
If you are just getting cheap cat food just to give as an occasional treat, go for it, but be aware that most of it is junk food and should only be given as a treat as it will provide no benefit to the chickens.