Not sure what else to say. Somebody in my guild found it a few weeks ago and out of curiosity I downed a bottle on my Pandaren Rogue and Pandaren Death Knight. In both cases the debuff simply disappeared the next time I logged onto them.
After seeing the poison added as an objective in the trading post, I decided to try again and drank it on my main. Again, the debuff simply disappeared. I don’t have a precise time when.
I’ve heard that dying removes the debuff, but from what I saw this isn’t the case; my main died a few times after imbibing the poison but kept the debuff when returning to life. The debuff was simply gone one time when I logged in without killing me as advertised.