(in my version it's on appendMessagesToCase where the code reads:

message = {
      author: message_record.getValue('author', 'messages') === customer_id ? 'You' : message_record.getText('author', 'messages')
   ,  text: self.stripHtmlFromMessage(message_record.getValue('message', 'messages'))
   ,  messageDate: nlapiDateToString(message_date, 'timeofday')
   ,  internalid: message_record.getValue('internalid', 'messages')
   ,  initialMessage: false
   };