What a petty, spiteful, and idiotic way to go about this. It's truly pathetic. There is nothing to gain from downvoting, and yet, out of jealousy, those who feel wronged will do it anyway. All we can do is hope that good people will win out in the end and counteract their bad feelings with good feelings.
There is plenty to gain from downvoting. It keeps the reward pool healthy, it democratizes and diversifies the distribution of rewards, and also there is a curation reward. Who's not to like downvotes?
There is a downside though. There are people who own a lot of stake, and if they don't like you, they can strike your posts down one by one, making you lose all your hopes of ever getting rewards from anything you post, no matter how good the quality is.
Chipping away a small fraction from the potential rewards of someone's selfie because it doesn't look like worth it is not comparable though.
Such a nice and good comment 😘