It'll do until we have a better standard warning.

A standard warning would be good to have. It feels awkward trying to come up with a warning without knowing precisely what is to be warned about. In particular it isn't clear whether you would have a strong preference (ie. outright insistence) that the warning doesn't include specific detail that Roko's Basilisk is involved. After all, some would reason that just mentioning the concept brings it to mind and itself causes potential harm (ie. You've already made them lose the game).

Unfortunately (or perhaps fortunately) all such "Information Hazard" warnings are not going to be particularly ambiguous because there just aren't enough other things that are given that label.