Show the CTAs only to users with the wikilambda-abstract-optin right, with the permission check enforced server-side so that the CTA markup is not emitted at all for unprivileged readers.

CSS-hiding is explicitly not acceptable, because it would leak the existence of opt-ins (or of potential opt-ins, on the special page) to any reader willing to view the page source. The permission check must decide whether the markup is generated, not merely whether it is visible.