When a single letter s or d is added to a word, the entire new word is highlighted as if the entire word would be completely new. It would help a lot by differentiating between letters that have been present before (say, light-green) and letters that have been added anew (dark green), like this:
or maybe weatherwhether. Thus highlighting two characters on each side.
As I currently see it, criteria for highlighting could be as follows:
light red/green means: this text remains definitely unchanged, it is only here to get a better context. It might contain additions/deletions like
wetherwhether. But not necessarily each and every unchanged character or substring is colored light that remains unchanged.dark red/green means everything else. Thus, this text is deleted/new, or it is too complex to explain the precise differences and thus we assume to delete it completely and retype it. Otherwise, cases like suggested by @Juhana would appear.
within a word the number of changes between light/dark is limited to a few changes only.
The reason why your edit looks a bit too far, is that the change of the a and h are "crossed".
Edit: This is not a duplicate. I am suggesting here an additional color/shade to permit a better differentiation between actually new characters and the word-context.
My suggestion thus would change the current diff only by changing some text from light-green to dark green.
Edit: Here is an example I just had while reviewing. It took my quite a while to see the actual difference. A better highlighting would help here:
