People shouldn't use git without having configured that. It would prevent incorrect commits landing in public repositories. Actually git defaults to some made-up local git author if it's not set, and that's less useful and sometimes invalid, provoking git-fsck errors.

Git explicitly shows a "Committer" line when typing the commit message if it chooses a default, so I also find not setting one globally and getting this reminder to be more useful:

  # Please enter the commit message for your changes. Lines starting
  # with '#' will be ignored, and an empty message aborts the commit.
  #
  # Committer: Ben Alpert <[email protected]>
  #
  # On branch master
  # Your branch is up-to-date with 'origin/master'.
  #

I agree. A potential middle ground would be a small button that lets them skip that screen with a second confirmation dialog box with a warning about it.