You're saying something different.
He's saying the guy got banned because to him it looks suspect if there is 17 instances of Diablo originating from 1 IP address.
You're saying if one account gets banned they're going to trawl through all the other accounts attached to the IP address of the banned account and ban any of the others they think are related.
They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP They don't ban by IP
They don't ban by IP.
There's a good chance you have a dynamic IP address. That makes IP banning pretty useless
They don't ban by IP