PS RE:

http://www.freekindlebooks.org/Dev/StringMatch/hkdiff.txt

Attempting to hand-score the kinds of edits one would need to do on hkdiff.txt, it seems to me like an intelligent editor could present “Choose A” vs. “Choose B” alternatives about 85% of the time, whereas the other 15% of the time a more complicated interface would have to be presented – or else the editor just punts and points to the text and says “You Fix It! (which is basically the approach my current choice of editor takes 100% of the time ;-)

However, if the editor gives a “Choose A” vs. “Choose B” interface sometimes the editor (and/or the user) is going to be deceived because what looks like an A/B choice really ISN’T.  For example a hypothetical example:

…. one { must | MUST } be careful!

And the correct answer is neither A nor B but rather C == _must_