The DHF has a limited amount of funds (which voting for the comments increase, as @blocktrades told you).
There is a cap on the total DHF budget. As I indicated in my other comment, the stabilizer has consistently maxed it out. The comment rewards are in addition, to supplement DHF funds, not instead.
RE: The main excuse for malicious down-voting is "Over-Rewarded Content..." What about the account making $10k+ PER DAY in spam comments?