I wanted to dig back through some of my old archives of screenshots and found a pretty big smoking gun that pet buff messages were always classic.
Here is a link to a screenshot archive:
https://web.archive.org/web/20010729...misc_photo.htm
Note that the wayback date is July of 2001, but there are older images.
Go to the bottom and under 'Xzandar' images, click on '2. Reaching lvl 50'. The image link will jump to a 2003 archived version, but the original link name is :
https://web.archive.org/web/20010729...ing_lvl_50.jpg
Here is a new hosting of the image:
[You must be logged in to view images. Log in or Register.]
A message is shown saying:
Your pet's Pact of Shadow spell has worn off.
The UI is older but I believe was still active / supported in Luclin, however look at the wording on the level gain:
You
raise a level! Welcome to level 50!
That is an older version of leveling text, I know from later log files of mcoy's that it is what we see now:
From his 'Expired' character name log:
[Sun Nov 11 15:33:53 2001] You
have gained a level! Welcome to level 21!
From his 'Qien' character name log:
[Mon Dec 03 07:56:18 2001] You
have gained a level! Welcome to level 52!
[Wed Dec 12 01:41:33 2001] You
have gained a level! Welcome to level 52!
[Sat Jan 26 23:51:09 2002] You
have gained a level! Welcome to level 53!
[Wed Jul 10 21:17:02 2002] You
have gained a level! Welcome to level 55!
If you even look at a later image in the series here:
https://web.archive.org/web/20040706...ne_of_hate.jpg
[You must be logged in to view images. Log in or Register.]
He has gained experience into the level, and I do not even see a blue bar in the experience bar (he appears to have slight yellow into next bubble... the nipple as we all called it back in the day).
But MOST importantly, there is a line of text that is not indented after it wraps. This was a change in the 8/9/2000 patch note during Kunark:
So at the very least these messages were in place before this patch, if not since original release of product.
Is this still an open issue? I don't believe you've added these back in as I remember not knowing if some of my mage pet's buffs wore off or not.
Hopefully this will eliminate any doubt about the messages?