A far-right Austrian who received donations from and communicated with the Christchurch terrorist prior to the 2019 attack has had his X account restored, with X owner Elon Musk replying to one of his tweets.

The founder of the so-called Identitarian Movement, Martin Sellner, who preaches the superiority of European ethnic groups, was banned from Twitter in 2020 under the former management along with dozens of other accounts linked to the movement amid criticism over the platform’s handling of extremist content.

Sellner was subjected to searches by Austrian authorities in 2019 on suspicion that he was cooperating with the Christchurch terrorist, Brenton Tarrant, and part of a terrorist organisation. Sellner has denied involvement in the attack.

It was revealed that Tarrant had made a €1,500 (A$2,487) donation to Sellner’s Identitarian organisation, and that the two had exchanged friendly emails in 2018, including Sellner inviting Tarrant to join him for a beer or coffee if he ever came to Austria.

Tarrant did visit Austria in 2018, but Sellner denies that the pair met.

Sellner praised Musk for restoring his X account last week, where he now has a blue tick associated with paid accounts and has 51,000 followers.

“I’m happy and grateful to be back on Twitter/X. I would especially like to thank Musk for making this platform more open again,” he said, according to an English translation of his tweet. “Hope the trend continues and everyone else who has been banned comes back.”

After Sellner posted a video related to Swiss police shutting down an event he was speaking at in the Swiss canton of Aargau and stating he had been banned from Aargau for two months, Musk replied “Is this legal?”.

Last month it was reported Germany was considering banning Sellner from entry to the country.

Dr Josh Roose, an expert in extremism at Deakin university, said Sellner’s account is the latest in a long line of far-right accounts, including the leader of the National Socialist Network in Australia, being allowed back on X under Musk.

“Coincidentally all of them in some way, shape or form interacted with Brenton,” he said.

“Now that these groups have come back and since they’ve been allowed back on the platform, they all follow each other’s accounts and they’ve linked internationally. So that’s also enabled the movement to build links and build contacts.”

X has been contacted for comment. In a fiery interview with former CNN anchor Don Lemon this week, Musk defended keeping up several antisemitic and racist posts on the platform, stating they were not illegal.

“So, Don, you love censorship, is what you’re saying?” Musk said.

Lemon replied that he believed in moderation, to which Musk replied: “Moderation is a propaganda word for censorship.”

If a post was illegal, “we’re going to take it down”, said Musk, adding that if it did not break the law, “we’re putting our thumb on the scale or being censors”.

Roose said while that might meet his reading of freedom of speech in the US, the accounts were originally removed for spreading of hate and attempts to inspire fear online and nothing had changed.

“While it’s not surprising, it just signals … it’s an enabling influence that provides these movements with a platform to spread hate.”

In January, the eSafety commissioner, Julie Inman Grant, revealed that, based on data provided to her by X between November 2022 and May 2023, X had reinstated 6,103 Australian accounts, including 194 that were suspended for violating what was then X’s hateful conduct policy.

“A number of these reinstated users were previously banned for online hate,” Inman Grant said at the time. If you let the worst offenders back on while at the same time significantly reducing trust and safety personnel … there are clear concerns about the implications for the safety of users.”

X was among half a dozen tech platforms this week issued with legal notices by Australian’s online safety regulator asking how they are taking action against extremist and terror-related material on their platforms. Grant said the video from the Christchurch massacre was still circulating online.

The platforms could be issued with fines for failing to respond to the notices within 49 days.

Roose said governments were reluctant to take “real action”, and while there had been speculation about Australia following the US in a potential ban of TikTok over security concerns, there was no real threat of X being banned for failing to tackle extremism on the platform, if that is what eSafety’s notices find.

“It comes down to the willingness to take decisive action based on leadership and an understanding of the basics and citizenship because you cannot get away in real life we are getting away with online and that is what’s corrosive to democracy … which is meant to be founded on mutual respect and recognition.”