> With vc-diff (similar, diff-buffer-with-file) you are diffing whatever
> you have against VC (or file), there is little point to edit via the
> diff, and you'd more likley just save this to file or an email. So in
> those cases the buffer being read-only makes more sense.
Sounds like you missed the new feature: committing a patch (C-v C-v in a
vc-diff buffer). You would usually edit it as well.
I really hope you typoed that, rebinding C-v to something other than
scrolling is a beyond terrible idea.