That's true, but they did need special permission to leep the identities of the moderators anonymous:
This, Reddit’s spokesperson notes, is “a significant departure from normal Supreme Court procedure.” The Electronic Frontier Foundation, a nonprofit defending online privacy, championed the court’s decision to allow moderators to contribute comments anonymously.
“We’re happy the Supreme Court recognized the First Amendment rights of Reddit moderators to speak to the court about their concerns,” EFF’s senior staff attorney, Sophia Cope, told Ars. “It is quite understandable why those individuals may be hesitant to identify themselves should they be subject to liability in the future for moderating others’ speech on Reddit.”
I'd note both the EFF and Reddit said this was unusual.
I think this is a catastrophy of American exceptionalism, really American narcissism. The idea that the provenance of ideas doesn't matter is insane to anyone who voted for Mr. Splashypants. How can you expect amicus briefs to the highest court in the land to become anything besides spam if they don't have attribution?