Hopefully Anonymous used the term and I asked him to elaborate on it. His comment is reproduced below:
That’s a good prompt. Maybe it will help if I list some things that tend to be anti-knowledge playspaces.

-Racial differences in behavior
-Global Warming
-What makes a good leader

And areas of science that seem to me to be more productive epistemological spaces even though they could have turned into anti-knowledge playspaces:

-population genetics
-(I would name more but out of time/energy/inclination)

In general I think anti-knowledge playspaces tend to be topics where two factions emerge whose constituencies add up to be a hegemonic force in the discussion, both of whom have their positions made up more by politically correct policing than by solid empiricism, and both sides probably suborn subpopulation identities who feel they can win in status games if their side either wins out by luck of being right or by show of force in dominating their opponents in the discussion space. I think it’s a bit of a 2 side competition that’s also a coordination against third parties that aren’t explicitly identified (the pageant element is a soft nontransparency, that the pageant element is to take social attention away from third parties is a hard nontransparency).