This must be the reason every piracy community I know has strict rules about not requesting specific titles. Even if they had the IPs, I'm not sure what they could prosecute, especially considering the number of users who use a VPN.
Honestly, it’s not worth their time to come after the people pirating, but rather, the people enabling the piracy to take place. In other words, users have nothing to worry about, it’s the websites hosting the torrents, that need to worry.
Or the ISPs in this case. They want the information about the pirates to use them as witnesses to show that the ISP didn't terminate copyright infringing users, even when notified dozens of times and to show that the ISPs benefitted from these practices by retaining them as paying customers.