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Twitter says it has stopped enforcing its policy on misleading information about coronavirus.
According to the company's website, it stopped taking action against tweets breaching its Covid rules, on Wednesday, 23 November.
Twitter had previously reported suspending more than 11,000 accounts for Covid misinformation as of September this year.
BBC News has approached Twitter for comment.
Its other policies on false information remain on Twitter's website, without a similar notice saying they will no longer be enforced.
Under its Covid-specific policy, Twitter operated a "five-strike system" for accounts posting "demonstrably false or misleading" content that may "lead to significant risk of harm" - such as exposure to Covid or damage to public health systems.
No action would be taken against accounts tweeting disinformation once. But repeat offenders could be suspended for a matter of hours, days - or even indefinitely, if they received five strikes against their account.
Though he says the Covid reporting system on Twitter was never perfect, Dr Stephen Griffin of The University of Leeds School of Medicine says it was reassuring to know that many thousands of accounts spreading disinformation had been removed since 2020.
'Amnesty begins'
Now, some of those who fell foul of the rules are returning to the website.
For example, Twitter has reinstated the personal account of US congresswoman Marjorie Taylor Greene, banned in January.
Millions of users voted for the reinstatement of suspended accounts in a Twitter poll, causing boss Elon Musk to tweet: "The people have spoken... amnesty begins next week."
The Tesla chief executive has vowed to make Twitter a hub for free speech online following his $44bn (£37bn) purchase.
Analysis from Rachel Schraer, BBC Reality Check
Criticisms the platform has been slow to act on false or unproven health claims are nothing new.
Even when Twitter did introduce an option to report misleading posts in the summer of 2021 - something it now seems to be rowing back on - I heard from dozens of people who said the process was unclear and the option didn't always seem to be available.
But the site did seem to be trying to get a grip on some of its most potentially harmful posts, removing more than 10,000 accounts - like Dr Robert Malone, whose message Covid vaccines are ineffective or very dangerous is contradicted by the overwhelming weight of evidence.
Now the direction at Twitter HQ is changing, the question is whether these accounts will return or new ones will be emboldened to share incorrect information, that could influence the decisions people make about their health.