Strange thing with RT 3.4.2

Hi list, last week when I was using root account to check one of our opened tickets, I saw a historical tickets list within the ticket display page.
In that list,there are some tickets created by the same creator who created the ticket I was checking.
And the strange thing is that I didn’t see any such kind of list within tickets created by other user accounts.
Then I tried to check privilege things but I didn’t work out.No privilege change was done.
We use RT 3.4.2 for more than one year.I haven’t ever seen such kind of list before.
Is there anyone who faced the same problem before?
Thanks in advance.