Twitter employees secretly censored negative comments made towards President Obama during a Q&A session on the platform in 2015.

Sources speaking to BuzzFeed News say then-Twitter CEO Dick Costolo “secretly ordered employees to filter out abusive and hateful replies” during the May 2015 #AskPOTUS event.

One team of employees was asked to create and deploy an algorithm that would “filter out abusive language,” while a second was tasked with manually censoring tweets.

According to BuzzFeed writer Charlie Warzel, two sources also revealed that certain senior employees were kept in the dark over fear “they would object to the decision.” Several employees, who adhered to Twitter’s alleged policy of unfettered speech, are said to have become upset upon learning of the decision.

Another source indicated similar moves were taken for a Q&A with Caitlyn Jenner.

Costolo responded on Twitter Thursday by labeling the claim “nonsense,” “false” and “absurd.”

2/ shows a lack of understanding of the very basics of how trust and safety works at Twitter. Sensationalist nonsense. — dick costolo (@dickc) August 11, 2016

In an official blog post on the issue Twitter failed to deny the accusation, instead opting to accuse the article of containing “inaccuracies” and “unfair portrayals.”

In response to today’s BuzzFeed story on safety, we were contacted just last night for comment and obviously had not seen any part of the story until we read it today. We feel there are inaccuracies in the details and unfair portrayals but rather than go back and forth with BuzzFeed, we are going to continue our work on making Twitter a safer place. There is a lot of work to do but please know we are committed, focused, and will have updates to share soon.

This latest story comes on the heels of several other controversies concerning the platform’s handling of speech related issues.

Gay libertarian journalist Milo Yiannopoulos was permanently banned from the site last month after Twitter accused him of “inciting” users to make abusive comments towards Hollywood actress Leslie Jones. Twitter has thus far failed to show evidence backing their claim and has been themselves accused of selective enforcement given provable incitement by Jones herself.

A growing list of examples and statements by former employees suggests that both Twitter and Facebook are favoring left-leaning users over conservatives.

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