If you're the sort of person who would take advantage of such knowledge to engage in dangerous activities, does that increase the probability that your reported time of death will be really soon?

Absolutely. Note the parenthetical. The grandparent adopted the policy of ignoring this kind of consideration for the purpose of exploring the implied tangent a little further. I actually think not actively avoiding death, particularly death by the means predicted, is a mistake.

On the other hand, if you're the kind of person who (on discovering that you will die in a plane crash) takes care to avoid plane crashes, wouldn't that increase your expected life span?

Moreover, these two attitudes - avoiding plane crashes and engaging in non-plane-related risky activities - are not mutually exclusive.