Well, my idea is this:
The nine year olds are interested in the Backrooms because of something they see on the internet. We can't do anything about that, but we can get rid of them before any issues arise. If we evaluate them before they make anything, we can see if they are under 13 before any issues rise.
For the partygoer roleplayers, the solution is easier: we simply get rid of them via a ban. That easy.
For Zalgo text users, we simply edit or report their pages so there isn't Zalgo text. We then tell them not to use it, or their page gets deleted.
Vandals are a little trickier, but doable: A ban. If anyone gets any ideas, we can ban them as well. That, or we can vandalize their pages so they know what it's like. >:)
A separate solution for each. That's my side of the story.