How did YouTube make all the top-ranked comments wholesome and funny?

Since YouTube launched in 2005, it has provided a comment section for its videos. But for many years, those comments were an unreadable cesspool of toxicity. "Some of the comments on YouTube make you weep for the future of humanity just for the spelling alone, never mind the obscenity and the naked hatred," Lev Grossman wrote in 2006. In 2009, The Guardian described them as a “hotbed of infantile debate and unashamed ignorance — with the occasional burst of wit shining through.”

But as YouTube approaches its seventeenth birthday, its comments aren’t nearly as awful as they used to be.

What changed? — That’s a question for Nikhil Dandekar, an engineering manager at Google who leads the team that works on comments quality. He confirmed that his team has been working to make YouTube comments more pleasant. “As with everything hard, it takes a lot of focus, hard work and good decision-making to transform a space,” he tweeted on Monday in response to a tweet from Patrick Collison, the CEO of payment company Stripe.

Dandekar hasn’t revealed the details of his team’s work, though, and if he does, it won’t be on Twitter (“maybe in a future blogpost” he tweeted).

According to Eugene Brevado, who leads the Learned Systems group at Google Brain, the solution was lots of labeled data and deep neural networks. Even though many YouTube comments are quite funny, the team didn’t necessarily optimize for humor. Instead, what they looked for was “probably some combination of toxicity, rating, and long term value to users,” Brevado shared. Though creators have some control over comment sections (like deleting comments and pinning comments), their efforts to sculpt the sentiment of their comments can only go so far.

Another manipulation to make the video-sharing site more positive occurred in November when YouTube removed public dislike counts in an effort to curb “coordinated dislike attacks” (though a Chrome extension cropped up to allow viewers to view the dislikes).

It’s encouraging to see machine learning make the internet a little bit better, but YouTube’s motivation to highlight positive comments may not be entirely altruistic. Funny and harmless comments make a viewer chuckle and move onto another video (or another ad) while controversial comments are more likely to inspire a response. But YouTube doesn’t make money when people have meaningful discourse in the depths of the comments section — it makes money by putting ads in front of eyeballs.