Now that I know what TS means, I am truly not fussed either way but if pushed to cast a vote, I say OP because more people appear to recognise what that is.
It is an indicator for who started the thread. If you scroll up you will see TS on Nifty's avatar, this is because he started this thread.
This thread has more detail: https://www.backyardchickens.com/threads/new-thread-starter-ts-on-avatar.1210925/#post-19267694