It doesn't guarantee that causality is protected, but it certainly seems pretty suggestive that GR creates a big infeasibility region for positive-mass objects

It doesn't guarantee that causality is protected, but it certainly seems pretty suggestive that GR creates a big infeasibility region for positive-mass objects (outside of the future-past light cone). There are ways you could still violate causality despite this restriction, but it makes it a lot harder. There's no particular reason we couldn't have a ++++ spacetime, which wouldn't have this form of causal censorship, so I count this as one more piece of evidence towards "maybe causality violation is impossible".