Steem is not a "Site" and there are no Terms & Conditions or any other such agreement that people enter into with Steem and there will never be such a thing as it goes completely against the vision and ethos of Steem, something that I have no doubt both Steemit AND the largest stakeholders will endeavor to maintain at any cost and the singular reason why downvoting exists is to directly do what you think is "abusive", read the whitepaper.