Chat Assignment Setting
Under your Settings > Integrations > Chat > Assignments you will find "Un-assign on reply" option. Note that the option will be enabled by default and it will be valid for Messenger Tickets and Chat Tickets as well.
When "Un-assign on reply" option is enabled, it will automatically unassign all tickets that have received a reply and at the same time Agent that ticket was assigned to is not set as available for chat.
This should help everyone reduce the response time for some chat tickets.