[I'll be moderately impressed if your world is covering all of its bases so well that a randomly sampled average person from another, moderately lower-tech world knows nothing very valuable or useful to your world.  But I suppose most valuable knowledge of that kind is valuable whether the person is telling the truth about how they got it or not?  It is nice not to be thought insane, though, especially when one is not insane.]

[I'll be moderately impressed if your world is covering all of its bases so well that a randomly sampled average person from another, moderately lower-tech world knows nothing very valuable or useful to your world.  But I suppose most valuable knowledge of that kind is valuable whether or not the person is telling the truth about how they got it?  It is nice not to be thought insane, though, especially when one is not insane.]