I gave up on checking upvotes and downvotes to comments on reddit a long time ago. After Reddit user Unidan got caught manipulating his own comments with several accounts while downvoting other "competing" comments or anything he didn't want to be visible.
So if a normal user can do that what can the ones responsible for the website do? Fact is, we don't know since its centralized. If not enough people care it remains hidden to the public what happened (why my steemit related posts there for example get downvoted usually) or why someone else comment got -25 downvotes from someone who might or might not be using bots/more accounts.
Here on Steemit we can see which accounts downvote what, or try to silence someone or try to do anything shady. Its all registered on the blockchain and without a good cause it usually doesn't get flagged. Of course anonymous accounts can still remain anonymous and try to do bot-flagging, etc but it at least re-assures you that your post/comment wasn't flagged because 20 different users disliked it, but rather some weird accounts who probably are connected to eachother. Plus here they have something to lose when voting against everyone else.