I'd like to point out that with the reputation system, downvotes are not simply the inverse of upvotes. This is because downvotes can harm the reputation of users with less rep than you, but not those with more than you. It's asymmetrical, favoring the strong over the weak.
There's also one that's incentivized and not the other. We need an upvote, downvote and a flag. Upvote/downvote on the blockchain, flagging only steemit based.