If you need to mute a chat user, hover over a message from that user and click the 3 dots that appear on the right-hand side of the message, and select 'Mute'.
You will no longer be able to see messages from that user. If you wish to unmute a user, you can do so from the chat menu in settings.
To get there, click on the 3 dots in the upper right corner of Pro, then select settings then chat. In this menu, you can see the name of the user, when you muted them, and when that mute expires, if applicable. If you wish to manually unmute a user, click on the corresponding "Delete" link in the 'Action' column.
You will now see that user's chat comments again.