Banned Users
Banning a User
It is possible to ban a user from either the Chat window, Mod Tools Auto Mod queue or the PUSH Console
The effect of banning a user is:
The removal of all messages they have contributed to Chat for all users, with the exception of the offending user
New messages from the banned user are no longer posted to Chat
The banned user receives no notification of the ban and appears to post as normal from their Chat window - in other words a shadowban
From the Chat window
To ban a message from the Chat window, hover your mouse over the intended comment then select the No Entry icon:

From the Auto Mod queue
See Auto Mod.
From the PUSH Console
See Chat Banned Users.
Unbanning a User
It is possible to unban a user from either the Mod Tools, or from the PUSH Console.
Unban from Mod Tools
From Chat, select the Chat settings cog then select Mod Tools
Choose Banned Users from the selector
Select Unban User for the user to unban
Unban from PUSH Console
See Chat Banned Users.