You can block a user in chat if you don't want to see what they write. To do so, hover over the user's avatar, and click on the "Block" button in the user info popup that appears. A system message will be sent in the chat where you did the blocking. Only you and admins will be able to see this message.
When someone is blocked, you will only see their messages as "{user} said something." The block is only effective on your own account; all other users who don't have the person blocked can still see their messages. The blocked user will not be able to send you private chat invites.
If you want to unblock someone, hover over their name in messages they've sent, and click "Unblock" on the user info popup that appears. Please note you cannot immediately unblock a user after blocking them; you need to wait several minutes before you can unblock the user.
