> I'm guessing one disadvantage is the method of diff is hard-coded into the patch. It would be good to switch to word-diff, or ignore whitespace, but I'd imagine these could be applied as transformations on the generic format.

The plugin I use in Thunderbird can switch between unified, context, and side-by-side diff views based on the same email. Adding the transformations you mentioned could be done.

But one limitation that email has over other review tools is the lack of ability to expand the view of the context within the client. The only way I could think of is to have git format-patch generate the diff with the entire context included and then have the client limit the display of that context. But that not have a reasonable fallback for those using clients that aren't capable or configured to do that.

Which plugin are you using? it seems life-changing to me

This is the one I'm using: https://github.com/Qeole/colorediffs. I installed it several years ago, so I'm not entirely sure whether you can install it on a current version of Thunderbird, but it is still working with my installation.

I might try it out as well! Thanks for it.