No, you got me wrong: only if the hashCode of two Addresses is the same do we sort them by their natural order. This does not affect the probability of neighbors being in the same datacenter. Choosing neighbors left or right also does not have any influence on this, but it would be bad from a cycles point of view: if everybody looks “forward” then cycles will be formed around the ring (depending on whether or not the ring size is a prime etc.), if everybody looks forward and backward then most cycles will be of size two (i.e. monitoring pairs watching each other mutually).

On that other note: I think it would make sense to make this hashing be skippable by configuration for those who want to prefer local monitors (in Address’ natural order), but that could also be a later addition.