The latest closures represent a reversal in thinking for Steve Huffman, who replaced Ellen Pao as chief executive officer for the online forum on July 10.

Many of the newly banned sections contain racially charged content, and make "Reddit worse for everyone else," Huffman says. Less than a week after taking over as CEO, Huffman responded to a question about one of these forums, saying, "The content there is offensive to many, but does not violate our current rules for banning." Huffman, the site's co-founder, now says Reddit is also banning communities dedicated to animated child pornography.

Reddit faces a difficult challenge in balancing the desire from its outspoken users to protect free speech with creating an environment that's hospitable to other readers and advertisers. The company, backed by Silicon Valley venture capitalists and the parent company of publisher Condé Nast, describes itself as "the front page of the Internet."