How would they even be able to fix it, short of redirecting all their domains to stackexchange.com subdomains (and causing a colossal branding mess and making e

How would they even be able to fix it, short of redirecting all their domains to stackexchange.com subdomains (and causing a colossal branding mess and making everyone mad)? Almost by definition, anything that would allow them to know you've accepted cookies on a different domain would be a form of tracking that all the anti-tracking stuff would clamp down on.