Is it possible to remove the CLOSED button from an esclation reviewer in CA?

Greetings 

Yes - the 'Close' button in Escalation review is controlled by the Department permission: 'Change Escalation Status' 

This permission allows or denies the ability to close escalated items and re-assign them to other escalation reviewers. It is useful when the escalation reviewer has finished work on an item. It effectively prevents any further actions performed on it unless it is re-escalated. Helps reviewers sort items that have been completed. 

Remember - a reviewer may be in multiple roles. If only one role has the 'Change Escalation Status' checked, they will see the Close option.

See screenshots.

Cheers
Andre