The very first merit transaction was 1 merit sent from theymos to AdolfinWolf for this topic:
What is the function of the "Merit" score?. This transaction was made around an hour before theymos started the topic announcing the merit system.
Nearly found it, but still need details of first reverted merits!
theymos never actually posted himself to say he removed QuestionAuthority as a source, but QA confirmed it in this post:
Apologies to all concerned, I will no longer be handing out merit in this thread. Theymos removed me as a merit source because he disagreed with the way I spent my merit. I will leave this thread open and you can continue to post merit requests here if you like; however, I wont be answering them.
Good luck to all.
CBH
These merits were not reverted. You can still see them in a number of posts following this post by QA in the WO thread:
https://bitcointalk.org/index.php?topic=178336.msg46588186#msg46588186