I was initially indifferent-to-unconvinced about it but now I think it's one of the all-time great additions alongside pronouns. You still kinda have it because you can just upvote the person in the debate whose opinion you prefer if it gets to the point of debate which is a kind of relative downvote, but people actually having to come out and propose and then defend an objection is much healthier for everybody rather than nurturing silent resentments between users, and you can't just make a bunch of alts to downvote somebody you disagree with, especially for days, weeks, or months after an argument has happened. If you really dislike a person then the block button is there and if they're being bigoted then so is the report button.