Thanks MMM, I still have the comparison work from your original project - brilliant problem solving!
I've found all the differences in the above list. Most are single character changes or insertions, with just a few textual changes.
Oil trees become pine trees and a couple of other minor changes which do not appear to have a fundamental thought change.
For your info, a font change wouldn't trigger a hit in your algorithm because a font is merely a collection of glyphs which overlay the underlying unicode values.