The minimal required author format, as hinted to in this SO answer, is
Name <email>
In your case, this means you want to write
git commit --author="Name <email>" -m "whatever"
Per Willem D’Haeseleer’s comment, if you don’t have an email address, you can use <>
:
git commit --author="Name <>" -m "whatever"
As written on the git commit
man page that you linked to, if you supply anything less than that, it’s used as a search token to search through previous commits, looking for other commits by that author.