Presumably, by definition, someone who gets this date reference.By this definition, I wasn’t, but now I am! There is a clue at the beginning of my previous post for those who need a sign (language)....
Using the "ok, ok" and "sign (language)" clues of Tetzoo Quizzer, I figured out that it is a reference to Koko the gorilla who died on 19 June 2018 (the news articles about it all date from 21 June 2018). Very few people would know those dates by heart, so I guess a "real Zoochatter" is just someone with Google. But now anyone who reads this post can be a real Zoochatter.
Ah that sounds like about right. Thanks @Chlidonias. But I still don't understand how Koko's death is a joke?
I think it is supposed to be that the joke is that "only a Zoochatter will know this date by heart" not that the actual death is the joke.
Basically, the database holding the data for the site (including, pivotally, the gallery) was at capacity, so @Simon Hampel was forced to delete a sizeable chunk of the gallery (selecting those items which had the least views or comments), with the intention of reinstating the deleted items from a backup once more database space was available. Then his backups failed the net result being the loss of a LOT of photographs uploaded by members who are no longer present on the site, some of which (showing seldom-visited zoos, former exhibits or species no longer kept in captivity) were irreplaceable. My "Species We Have Lost" and Photographic Guide threads are all intended, in some small way, to encourage anyone who can fill gaps created by the Great Purge to do so.
Re. Jake's joke, I just did some searcing and came across @Jake1508's old account called 'Jake'. He joined Zoochat on that account on June 21 2018.