When you hardening security of an OS, you disabling any unessacery service/daemon, and try to not have any services listening to insecure networks.
Im not sure if the mdns (Bonjour) demon is open source, and even if i wouldnt use it in public networks. I think its running with very limited rights but dont forget:
Human make errors, and software is made by humans
(sry i dont have time to read the whole pdf atm, hope i understanded it right )