document.getElementsByTagName('main')[0].style.margin = '0 auto';

IMO (as someone who doesn't have to deal with the actual rendering) it would go a bit deeper into talking about deciding how to show what has changed. There's a lot of improvements that could be made there. e.g. "whitespace has changed here" so there's no real code changes involved.

Or "this big list of imports has changed, and code formatting has line-wrapped the list into different lines" - gitlab for example copes poorly with this. I'd love to just see a clean diff that highlights the additional import, and not just ten lines of changes caused by adding one line to a big list of imported symbols/functions.

(I say this, having done a vibe-port of the code to a browser extension, so the underlying concept works.)

something i'd really want to see from forges is alternate diff techniques: like AST diffing.