[InspiredIdiot]

Would you consider updating the site guidelines to explain this "just the diff" principle? It sounds like an important enough concept to be captured there. And it seems in some cases to supersede the "please use the original title" guideline so it's probably worth calling that out.

[Edit]

I wish I didn't have to continually edit myself but originally I used the term "editorialize" and I thought it had a more broad meaning of "exercise editorial discretion". While there is still an opinion involved in the edit. Something along the lines of "users of this site will already know X so it isn't part of the diff" I don't think it meets the stricter definition of editorializing. "Not part of the diff" is still cited as a justification for editing the title that I don't see covered in the current site guidelines.

[dang]

I think this case is a bit weird and you shouldn't generalize too much from it. I wouldn't put that principle in the guidelines, for the same reason. These are heuristics, not formal rules, and my comments are just trying to help people understand the intended spirit of the site.