Some people never ever let a hen hatch chicks. One hen was too young, or just a bad mother, and they judge all chickens the same.Not always true----I had several broody hens that almost died trying to protect their chicks, head skin picked clean to the skull, combs torn off, dead chicks with crushed skulls from being pecked. Not always Peaches and creams I promise. I feel the breed of chickens the broody is with effects what will happen. I personally never have that happen to my broody hens or chicks killed anymore because I do not let her and the chicks be with the flock for a long time---if ever.
I'd rather go by the norm, and realize that chickens are capable of doing what comes natural.
Unfortunately, we humans have bred natural instincts out of them. My broodies share a nest, and share chicks. I pay attention, but don't interfere.