It's quite simple. We never thought to check Hydrogen or Grand Moff or JCS of using similar IPs until a user requested it. The forum doesn't automatically notify us when more than one user uses the same IP-it is a manual check. Sometimes if we suspect it's a formerly banned user we check and other times we check because a user told us. We have thousands of accounts and loads created daily: we don't have the staff to check every account and to keep checking.
Our investigation abilities are very limited to only what we can see from the AdminCP. We have a very small budget and that goes to paying for the server and the domain name. Our staff are volunteers-they are not paid. We are a non-profit site and all the money we make through donations and ads is to pay the bills. We don't make that much though.
When it comes to multiple IPs on a user within a short time frame, we tend to thus assume guilt rather than innocence.
If we made a mistake, we are sorry, but we aren't out to get any users. We are doing the best we can. We aren't perfect, we will be the first to admit that.
We wish JCS the best though.