I personally find it a good system, not in an absolute sense but relatively speaking. It gives some idea how your node was received by the community.

But I agree that if you downvote a node, it is best to give a reason for it, so the "beneficiary" of your downvotes can learn from it.

That being said, nobody gets any better by artificially withholding downvotes, because it is the "politically correct thing to do" and since each monk can only downvote each node once, there is little risk of indvidually breaking the reputation of a monk.