I'm confused why everyone is pretending that a ban holds any meaning here. he probably already has a new account, it might have made sense to just silently ban him in the hope of imposing a minor cost on what you believe he is doing, but wasting your time addressing it imposed a far greater cost on you than him.
I understand how it can be confusing. The key factors in doing it this way are (1) the community regards older accounts, especially ones that have significant posting history, as more credible; and (2) doing it publicly rather than silently has transparency value.
