There are two ways moderators or higher can block people.
The first is blocking the user's individual account.
I'm using Sciz's for the sake of an example.
The second is by IP address, which is shown on every user's profile.
When a person is banned, people typically block both the account and the IP address. If the account is just blocked and Sciz wanted to create a second account, he could potentially create a new account under a different name and bypass his block, so all bans are IP bans, it's just that we undo the action it's something temporary.