People say upvotes/downvotes are harmless. They're not.

Every social media site uses them, and the reason isn't that they're a good invention. The reason is that they're psyop. Voting is a way of not having to come up with an actual argument/post but still get your feelings heard.
It will make people forget what they even wanted to say, and they'll learn to act on impulse. It's social media's way of saying "hey normie, wanna have an emotional tantrum but cant finish a sentence? push this mob mentality button and receive gratification!"
Due to Twitter's character limitations, people are already struggling to write anything meaningful on the Internet, and the downvote culture removes that need entirely.