To be clear, at the time I wasn’t really thinking about other people escalating the playfulness. That didn’t even occur to me as a thing which might happen, until I was thinking about it after the fact.
I didn’t have a particular community in mind. Wish I knew one. Well, other than an elementary school or some other childrens’ community—that would definitely qualify as supercritically playful, but has a bunch of other downsides.

I haven’t looked into this very deeply, but I suspect that some of this information is historical propaganda. In particular, when I shallowly looked into the famous slave ship diagram some years ago, it didn’t really add up, and I came away thinking it was likely propaganda from the abolitionists’ side. (… but I investigated only briefly and don’t remember the details, so take this with a lot of salt.) Some of the other things also have a propaganda vibe—e.g. the thing about slavery being bad for the economy, or about the sailors, or Clarkson giving an awfully heroic account of himself.