// Get the email subject and body
var subject = email.subject;
var body = email.body_text;

// Look for a ticket number in the subject (e.g., INC0000001)
var regex = /INC\d{7}/;
var match = regex.exec(subject);

if (match) {
  // A ticket number was found
  var ticketNumber = match[0];
  var incidentGR = new GlideRecord('incident');
  incidentGR.addQuery('number', ticketNumber);
incidentGR.addQuery('state','7'); // please add state of closed
  incidentGR.query();

  if (incidentGR.next()) {
    // Incident found, update its comments
    incidentGR.count = incidentGR.getValue('count')+1;
    incidentGR.update();
  } 
}

Use the above code inbound action.
create a new field in the table update the same in the code, and update table names as well.