rtvd,  Thanks for taking the time to post this patch and participate in the discussion.

This patch changes intentional, by-design behavior.  It would hurt difflib's performance and reduce its usability, by making the matches worse.  Subjectively worse, admittedly, but with many programmers sharing similar subjective views.  Read the comments in the source code and you'll get the gist.

And even a mathematician would dispute your assertion that there's no such thing as "interesting".  That's a pretty extreme view.