I never said that it compromises your anonymity just that it doesn't protect from the attacks that you need to worry about anymore than using Tor by itself does. The only attack adding a VPN before Tor protects from is if the attacker is at the end point and they try to work their way back to you by gathering log files one node at a time. Additionally it protects from membership enumeration, but that is unrelated. Regardless this topic thus far has been about the ISP's ability to see the plaintext of the data the user is loading, not about the ISP's ability to trace the users connection to its end point. Although related, these are two distinct areas. Adding a VPN prior to Tor will not make it so your encrypted traffic is less vulnerable to cryptanalysis (in either cases the encryption is not going to be broken) or fingerprinting attacks (in either case the attackers ability to fingerprint will be limited by Tor, not the VPN), so in short go fuck yourself.