

I’m not sure about markdown but plenty of IDEs can fold eg a method or a class. Off the top of my head I know Geany, Jetbrains, probably most gui text editors/IDEs do. Not sure about markdown specifically, I only use vim for markdown which I know can fold.
People already do this on “low-tech” levels ie community monitoring and alerts, but yes it’s not been done on particularly high-tech levels in a similar manner to the surveillance state