In this case, it's less about the actionability of going after the pirate and more about using them as a witness to go after the ISP with deeper pockets by showing they failed to kick pirating users off of their service. They don't care that they downloaded it, they care that the users knew they wouldn't get in trouble for piracy with that ISP and that the ISP benefited from that by keeping pirating users subscriptions active. Testimony from pirating users about why they chose that ISP and how even they knew the ISP wouldn't do anything to resolve copyright violation issues could be pretty helpful in court.

From the article:

In this week's filing, the film studios claim that six Redditors' IP address logs are “clearly relevant and proportional to the needs of the case" because the Reddit users all made comments that either establish “that Frontier has not reasonably implemented a policy for terminating repeat infringers sufficient for a safe harbor affirmative” or that “the ability to freely pirate without consequence was a draw to becoming a subscriber of Frontier."

Last year, a Reddit user wrote that they received 44 emails from Frontier threatening to cut off their service due to torrent downloads, but “if they didn’t do it after 44 emails ... they won’t."

In 2022, another Reddit user said that they had used Frontier DSL for years and “despite the shitty internet, they didn’t give a shit what I downloaded.”