jumboteam  @KevinTheJedi  That script was to hide the "Deleted by Agentname" line mention just above the first thread.
To delete the duplicate records use below query.
DELETE t1 
FROM ostno_thread_entry_email AS t1
INNER JOIN ostno_thread_entry_email AS t2 
WHERE 
    t1.id < t2.id AND 
    t1.thread_entry_id = t2.thread_entry_id;
	
Below script is to hide the "deleted by agentname" line. add this in header.inc file.
<script>
        $(document).ready(function() {
            $(".thread-event .type-icon:first").css(
              "display", "none");
              $(".thread-event .description:first").css(
              "display", "none");
        });
    </script>