Similar to the option to preserve the setting whilst moving between PRs, I'd really find it helpful if there was a "hide whitespace changes by default" option which would append w=1 to the "add your review" button link.

I basically never care about whitespace changes (I'm certainly not alone here in our team, but I'm not sure how global a stance this is) -- we have .editorconfig settings which help the team to be consistent and there are occasionally old files which have been auto-formatted, so of course it looks like the whole file changed. I typically find one of these about 1/2-way through a review, so have to scroll back up to the top to tick the box to hide whitespace changes.