UPDATE: Reviews section refreshed, redesigned, searchable: Go take a look
As has been said, we don't ban IP addresses as that's clumsy and results in collateral damage. We ban accounts (very rarely people) If duplicate accounts are reported to us or we spot them then we act. If anyone starts a new account while banned then we ban the account and extend the original ban. But we can only do that if we are made aware of them.
And I'll take this opportunity to point out that traditionally at this time of year all bans from say, now will be for the rest of the year so that we can all have a break from moderating to get some turkey and family time 🙂
Oh right, I have a nice report on some bigotry posts cooking nicely.
*gets writing*
Not that its ever happened to me but I dont think there's a realistic way of doing it unless sites get and record MAC addresses or similar.
Download mac address emulator... Un-banned

