Okay, I'm convinced. I think adding a comment along the lines of
"narrowing is not a minor mode, but its indicator is part of
mode-line-modes", would be helpful in case someone tries to "fix" your
change later.
> + (when (or (> (point-min) 1) (<= (point-max) (buffer-size)))
You should use buffer-narrowed-p instead of checking point min & max
here.
Have you assigned copyright for Emacs?