When Laura Loomer, a far-right activist, regained control of her Twitter account in late 2022, she knew whom to praise for her reinstatement.

“Thank you, Elon!” she wrote to Elon Musk, who had recently bought the social network. In another post, Ms. Loomer, who had been booted from the platform in 2018 for writing an anti-Muslim message, complimented Mr. Musk’s commitment to “free speech.”

Ms. Loomer is now sharing a different message about Mr. Musk. She and a prominent group of right-wing figures — many of whom have enjoyed more visibility on the platform, renamed X — are increasingly raising alarms about Mr. Musk’s influence over President-elect Donald J. Trump and what they characterize as his willingness to silence critics on his social network.

Apart from Ms. Loomer, high-profile conservatives including Charlie Kirk and Stephen K. Bannon have started speaking out against Mr. Musk or his policy positions. Batya Ungar-Sargon, the conservative opinion editor of Newsweek, recently called Mr. Musk a “shill” who censors opponents. Mike Davis, a lawyer close to Mr. Trump, told Mr. Musk on social media to “stay in your lane.”

Their criticism followed X’s moves to suspend or otherwise restrict dozens of accounts that raised concerns about Mr. Musk and blocked links to articles about him, citing violations of its terms of service. Over the weekend, Mr. Musk drew further ire from conservatives for using his X account to attack Nigel Farage, an ally of Mr. Trump and the head of Britain’s far-right Reform UK party.

Mr. Musk, 53, has rapidly vaporized some of the good will he built with Mr. Trump’s supporters after campaigning heavily for the Republican presidential candidate last year. Some right-wing personalities who championed Mr. Musk’s foray into Republican politics now say they feel deceived and worry that their agenda may be sidelined in favor of his own.

“As a loyal supporter of President Trump, I support him enough to sound the alarm on what’s becoming a liability,” Ms. Loomer said in an interview. Ms. Loomer, whose X account was temporarily suspended last month after she criticized Mr. Musk’s views on immigration, added, “You’re not allowed to question Elon, it seems, and the looming question is: Is Donald Trump going to step in before it creates a crisis for his administration?”

Mr. Musk and X did not respond to requests for comment. On Tuesday, Mr. Trump said Mr. Musk had “said some negative things” about politicians in Europe — the president-elect did not name Mr. Farage — but was “doing a good job.”

Mr. Musk’s falling-out with some on the far right stands out as he increasingly embraces more extreme parties and figures globally, including in Germany, where he has backed a political party with ties to neo-Nazis and plans to host a livestream with one of its leaders on Thursday. Some Trump fans, such as Alex Jones, the founder of the conspiracy-theory site Infowars, remain supportive of Mr. Musk and have said any dissent is aimed at undermining the incoming administration.

Still, the split raises questions about whether the billionaire and right-wing Trump supporters are allies of convenience. In some ways, Mr. Musk has become a target of the principles he has championed on X by allowing Ms. Loomer and others who were barred from the platform to return.

“Speech suppression on Elon Musk’s X is nothing new, and the claims of ‘free speech absolutism’ were always performative,” said Evelyn Douek, a Stanford Law School professor who studies the regulation of online speech. “It’s especially poetic that these charges are coming from someone like Loomer, whose account reinstatement was supposedly emblematic of the dawn of a new era on Twitter.”

Ms. Loomer, a two-time Republican congressional candidate who has described Islam as a “cancer,” broke from Mr. Musk a few days before Christmas after posting on X about her unhappiness with Sriram Krishnan, an Indian American venture capitalist whom Mr. Trump picked to advise on artificial intelligence. She said Mr. Krishnan supported expanding the use of H-1B visas to bring skilled foreign workers to U.S. companies, which she decried.

Mr. Musk, who has used the visas to hire workers at his companies, including Tesla, defended the program as a way to attract top talent from around the world. “I will go to war on this issue the likes of which you cannot possibly comprehend,” he said on X on Dec. 27.

As the argument escalated, Ms. Loomer and Mr. Bannon framed Mr. Musk’s views on foreign workers as an insult to Mr. Trump’s “Make America Great Again” base. They said Mr. Musk was beholden to his business interests, including Tesla’s ties to China, and questioned if it was appropriate for someone to hold such financial sway over their party. Mr. Musk spent more than $250 million to help Mr. Trump win the election.

Mr. Musk “became addicted to the adoration the rallies gave him in the run-up to Election Day,” Mr. Bannon said in a message to The New York Times. “But that quickly turned to derision when MAGA saw he thought of them as lazy and mediocre.”

On Dec. 26, X suspended Ms. Loomer’s account for 12 hours. In messages to Ms. Loomer, X said she had violated its terms of service by posting an image from the Federal Election Commission website that included the home addresses of political donors. X prohibits some personal information from being shared without a person’s permission, even if it can be publicly obtained.

Without additional explanation, X also removed Ms. Loomer’s check mark, which X users pay for so their accounts can get increased engagement and, in some cases, so they can receive a share of ad revenue.

That same day, Preston Parra, the chairman of Conservative PAC, a political action committee formed to support Mr. Trump’s policies, discovered that his X account had also lost its check mark.

He and Ms. Loomer were among more than 50 members of a group on X connected to Conservative PAC, many of whom had blasted H-1Bs or Mr. Musk. Every member’s account lost its check mark, suggesting that it was a “coordinated” move, Mr. Parra said.

“I voted for Trump — I didn’t vote for Elon,” he said in an interview, adding that many of the check marks were restored last weekend. Ms. Loomer said hers was restored Monday.

Anastasia Maria Loupis, a doctor in Denmark with more than 1.3 million followers on X who has called immigrants “terrorists,” said her account also lost its check mark on Dec. 30 after she criticized H-1B visas and Mr. Musk.

On Monday, she wrote that she would take legal action against X. Mr. Musk “acts like the grand savior of free speech,” Dr. Loupis said in a post, but bases decisions only on “his selfish ambitions for money & power.”

In a message to The Times, Dr. Loupis said there “is no valid reason for what they did to me,” adding that “it’s awful what’s been going on here the past weeks.”

Over the weekend, Mr. Musk faced fresh criticism for censorship when X blocked links to an investigative article by The Spectator, a conservative British publication, about an X account that some believed Mr. Musk secretly controlled. The article suggested that the account, @AdrianDittmann, was operated by a man in Fiji.

On Sunday, X suspended the accounts of the article’s author and two researchers who contributed to the piece. X had identified the article as “potentially harmful,” and messages sent to the journalist and researchers showed that X said they had violated its rules on sharing people’s personal information.

X has faced accusations of opposing free speech and acting like the site’s previous management, which blocked a New York Post article about Hunter Biden before the 2020 election.

“This is what old Twitter did to the New York Post,” wrote Stephen L. Miller, a right-wing commentator.

Matt McDonald, the U.S. managing editor at The Spectator, said there was an irony to Mr. Musk’s actions, particularly as he was “turning the world upside down in the name of free speech.”

“Perhaps X is not the free-speech paradise its more ardent fans believe it to be,” Mr. McDonald said in a statement.

Mr. Musk turned on Mr. Farage after the politician pushed back against Mr. Musk’s support of Tommy Robinson, an anti-immigration agitator with several criminal convictions who is currently in prison for contempt of court.

“The Reform Party needs a new leader,” Mr. Musk wrote on Sunday. “Farage doesn’t have what it takes.”

Over the weekend, Mr. Farage told news outlets that he had a good relationship with Mr. Musk, but hinted at some disagreements. A spokeswoman for Mr. Farage did not immediately have a comment.

Mr. Musk’s comments about Mr. Farage incensed Mr. Bannon and others who see the Briton as perhaps the best way of introducing populist policies in that country.

“Nigel Farage is the greatest living Englishman, having fought for 20 years to get his country’s sober sovereignty back,” Mr. Bannon said in a message.

Raheem Kassam, a former adviser to Mr. Farage and the editor of The National Pulse, a right-wing U.S. news outlet, responded more succinctly to Mr. Musk.

“You’re a moron,” he wrote on X, using an expletive.