Every day, the moderators of BlackPeopleTwitter—the Reddit forum devoted to screenshots of tweets from black people—sort through inboxes filled with jokes about cooking, dating, or watching Marvel movies. And according to moderator “DubTeeDub,” that also means dealing with a “never-ending stream of slurs.”

Being the most popular forum about black culture on an overwhelmingly white website that hosts a number of racist subreddits has brought other problems, too. There are the white people pretending to be black, and the disgruntled commenters who accuse the moderating team of posing as black themselves.

The forum’s millions of subscribers have been able to stay friendly in the comments on a post about cooking or dating, but if someone mentions a political issue like racial profiling, white people have flooded the comments to say they didn’t see what the big deal was. The problem only got worse if one of BlackPeopleTwitter’s posts was popular enough to make Reddit’s general front page.

This year, the moderators had an idea. What if they figured out who was actually black and then got rid of all the white people?

Starting on April 1, BlackPeopleTwitter’s moderators announced that only Reddit users who had verified that they were black could continue to post comments or threads on the subreddit. Black commenters could send in a photo of their forearm next to a sign with their username written on it. In return, they’d get a checkmark next to their profile verifying that they were black.

Everyone else, meanwhile, could no longer post on the forum.

The April Fool’s Day experiment outraged the right-wing internet and has shaken up how one of Reddit’s biggest forums deals with race.

With more than 3 million subscribers, BlackPeopleTwitter has become Reddit’s 59th most popular subreddit, according to Redditlist. The subreddit relies on a simple idea: screenshotting tweets, usually jokes, from black Twitter users.

“Black Twitter” has been a concept online since at least 2008, according to Mia Moody-Ramirez, a professor at Baylor University who co-authored a book studying black humor and Black Twitter. Black Twitter, Moody-Ramirez told The Daily Beast, is where black Twitter users can use humor to deal with difficult issues.

Black people are more represented in Twitter’s user base than they are in the population at large, according to Moody-Ramirez, making Black Twitter more visible. In 2010, Slate columnist Farhad Manjoo wrote about how black Twitter users “do seem to use Twitter differently from everyone else.”

“I cannot keep quiet about my obsession with Late Night Black People Twitter, an obsession I know some of you other white people share, because it is awesome,” Choire Sicha wrote for The Awl a decade ago.

That same interest in Black Twitter had pushed the subreddit to the top of Reddit. The April Fool’s Day plan to deal with the influx of non-black posters that popularity brought in went well at first. Hundreds of black posters sent in pictures of their forearms, and the moderators initially faced an “overwhelmingly positive response,” according to moderator DubTeeDub.

“Pretty much all our regular users, white, black, or whatever thought it was a great way to bring to light how POC voices are getting lost in the shuffle on a subreddit that’s ostensibly about black people and black culture,” DubTeeDub, who declined to give The Daily Beast any information about themselves, wrote in a Twitter direct message.

Eventually, non-black allies were allowed to apply for verification. A white user posted a picture of himself apologizing for “institutional racism and bland chicken.” An Asian-American guy posted a picture of his arm next to a sign praising Killmonger, the villain from Black Panther .

BlackPeopleTwitter’s moderators had initially planned to keep the experiment going for a week. By April 2, though, Reddit’s racist white subreddits—many of which have been “quarantined” off from the rest of the site for their hateful content—had heard about the new policy and flooded the moderators with even more racial slurs than usual. They also set up a new racist subreddit, “SubForWhitePeopleOnly,” which was meant to be only for white Reddit users.

“Don’t get mad when we vote back in segregation,” wrote one Reddit user.

The backlash to the BlackPeopleTwitter policy even inspired an InfoWars article from right-wing internet personality Paul Joseph Watson. Citing the non-black Reddit users who had asked to be verified to use the subreddit, Watson wrote that they were “humiliating” themselves.

“Remember folks, your white privilege entitles you to be blocked from entire Internet forums because segregation is progressive now!” Watson wrote.

Under pressure, the BlackPeopleTwitter pulled the ban on non-black users after three days, rather than keeping it place for the entire week. Still, much of the racial verification system is still in place.

Reddit didn’t respond to a request for comment.

In the past, the moderators had to close comments on politically heated threads. Now they turn those threads into “Country Club Mode,” a restricted posting system in which only verified users of any race are allowed to comment. Unverified users are still allowed to post in other threads.

The backlash from other parts of Reddit hasn’t stopped BlackPeopleTwitter users from trying to get verified. Other, non-black posters can still be verified as allies, while black posters who have verified their race still get a checkmark next to their name to “combat perceptions of digital blackface.” Faced with thousands of verification applications and a limit imposed by the Reddit system on how many people they can approve each day, the moderation team has brought on new people to deal with the flood of requests.