Voting power is based on steempower, the more power you have the more your vote counts.
This isn't the first time this kind of thing happened to me. I kind of like to post controversial stuff.
In one reply (not even a post) I imitated a bot,but in a funny way. One guy laughed so loud that he personnaly sent me a SteemDollar. Another guy downvoted me because he though I was a bot, I guess he didn't get the joke.