Twitter has unbanned and verified a prominent white nationalist

Twitter has unsuspended the account of Richard Spencer, the prominent white nationalist who coined the phrase "alt-right."

The social network booted him off the platform in November, during a broader crackdown on accounts linked to the "alt-right," a far-right political movement that includes racists and neo-Nazis among its members.

While others banned then remain banned, Spencer is now back. And Twitter says that he wasn't suspended for his political ideas - only because he had multiple accounts.

The social network told him that "creating serial and/or multiple accounts with overlapping use is a violation of the Twitter Rules," according to an email provided to Vox, and that he opted to have his main account unsuspended while his others remain banned.

Spencer's account has now also been verified by Twitter.

Spencer is known for coining the name "alt-right," which he has described as "an ideology around identity, European identity." The term has become an umbrella for far-right movements online, and rose to prominence as US President-elect Donald Trump seemed to find many alt-right supporters in his White House bid.

Critics of the movement come from both sides of the US political aisle, and have denounced the alt-right as racist, sexist, and homophobic.

"These are people who are trying to mainstream racism through cultural appropriation and manipulation," Republican strategist Rick Wilson told Business Insider in August.

Spencer gained mainstream notoriety in November, when he spoke at an alt-right conference in Washington DC less than two weeks after the presidential election. His speech ended with several callbacks to Nazi Germany, which were apparently met enthusiastically by the audience.

"As he finished, several audience members had their arms outstretched in a Nazi salute. Mr. Spencer called out: 'Hail Trump! Hail our people!' and then, 'Hail victory!' - the English translation of the Nazi exhortation 'Sieg Heil!,'" The New York Times reports. "The room shouted back."

Twitter has long struggled with how to deal with abusive users and those who espouse hateful politics. Historically it has been reluctant to police its users too heavily. But facing significant outcry over rampant abuse and trolling, it has more recently begun to take a more proactive approach to the tackling abuse.

Earlier in 2016, it booted off Breitbart editor Milo Yiannopoulos off the platform over connections to a harassment campaign that targeted Ghostbusters actor Leslie Jones.

Below, is Twitter's hateful conduct policy:

"You may not promote violence against or directly attack or threaten other people on the basis of race, ethnicity, national origin, sexual orientation, gender, gender identity, religious affiliation, age, disability, or disease. We also do not allow accounts whose primary purpose is inciting harm towards others on the basis of these categories."

The policy is fairly clear as to the kind of speech that is and is not acceptable. The decision to allow Spencer back onto the platform raises questions as to what Twitter actually considers acceptable behavior.

Disclosure: Rob price was a freelance worker for The Kernel, a media company formerly owned by Yiannopoulos.