“I don’t know why in this country it’s not allowed to make any kind of criticism of you,” said the student, wearing a long-sleeved blue polo shirt and appearing calm.

“In the past three to five years that I have been reading newspapers, I have seen no criticism of you, not even by the Assembly of Experts, whose duty is to criticize and supervise the performance of the leader,” he said, referring to the clerical body that chooses the country’s supreme leader.

Khamenei countered, “We welcome criticism. We never said not to criticize us. … There’s plenty of criticism that I receive,” according to accounts in state media and on opposition Web sites.

The boldness of Vahidnia’s comments underlines how Iran’s post-election turmoil has undermined the once rock-solid taboo against challenging the supreme leader.