I like thinking about “lightcone” as “all that we can ‘effect’, using ‘effect’ loosely to mean anything that we care about influencing given our decision theory (so e.g., potentially including acausal things)”.
Another way to put this is that the normal notion of lightcone is a limit on what we can causally effect under the known laws of physics, but there is a natural generalization to the whatever-we-decide-matters lightcone which can include acausal stuff.
[Even more off-topic]
I like thinking about “lightcone” as “all that we can ‘effect’, using ‘effect’ loosely to mean anything that we care about influencing given our decision theory (so e.g., potentially including acausal things)”.
Another way to put this is that the normal notion of lightcone is a limit on what we can causally effect under the known laws of physics, but there is a natural generalization to the whatever-we-decide-matters lightcone which can include acausal stuff.