Saw Socrates post this from another meme asking same question
"I don't think they can cancel out upvotes. I think imgflip just keeps track of how many upvotes and how many downvotes, and they're factored into the formula that determines the position of the meme relative to others in the Hot stream.
With comments, enough downvotes can hide the comment."
imgflip.com/i/11k64p