They Criticized Musk on X. Then Their Reach Collapsed.

Anastasia Maria Loupis runs a popular account on X that used to receive hundreds of thousands of views each day for her far-right commentary, conspiracy theories and antisemitic statements.

In late December, she criticized Elon Musk, the site’s owner, over his support for visa programs that many of President Trump’s supporters despise.

Her reach plummeted on X and never recovered.

When Mr. Musk purchased X in 2022, he promised to create a free speech haven and named himself a “free speech absolutist.”

Critics still feared that Mr. Musk would use his control of the app to pick and choose his favorites, amplifying voices he admired while suppressing people or topics he loathed.

The New York Times found three users on X who feuded with Mr. Musk in December only to see their reach on the social platform practically vanish overnight. The accounts are the starkest signs yet that Mr. Musk or others at the company have the power to punish critics and that they may be willing to use it, startling free speech advocates who hoped that the billionaire would be their champion.