Mute
From xat wiki
(MUTE) - Owners can ban silently
Mute power allows you to ban a user without them knowing. Guests in the chat will also not be able to see the ban message.
To mute a user: click on their name, click "Ban", and press the "Mute" button. To make sure the power isn't abused, you are only able to Mute for up to 1 hour at a time.
Note: You must be an owner to use this power.