guest post draft check-in: "The Information Theory of Passing"

Sophia verbally said I could republish her analysis from our email
exchange the other year after I run it by her for edits (which, note,
I haven't done yet)! This is not quite verbatim from the email, with a
link to Wikipedia math, changes to formatting (subscript twos, Unicode
almost-equals, bolded list items, italicized "etc.", en dashes) and a
couple very minor wording changes (just "very different prospect"
instead of "very very very", cut phrase "in the rest of the email").