When a bolt breaks/fractures, does it or can it harm other parts?
The usually don’t harm anything with them.
But when I have a bolt failure I typically replace the cam pin, firing pin and firing pin retaining pin as well.
Ive seen it where the broken lug has:
went down inside the lower and scarred/nicked the hammer spring.
scarred the inside of the upper receiver.
locked the gun up with a round in the chamber