I remain sceptical. External observation (something on the life cam lines) still cannot distinguish an hour of thinking about the stars' main sequence from an hour of thinking about cosplay lolis. And diaries have the big problem of self-reflection... not being entirely accurate.
I take it our hypothetical system would not simply assume that diaries are accurate records; they would (so to speak) ask the question "how likely is it that any given person would write this diary entry?" which is not at all the same as the question "how well does this diary entry, taken at face value, match the actual life of this person?".
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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