Clarify "real name" in contributor requirements

CONTRIBUTING.rst

@@ -130,11 +130,15 @@ If you agree to this for your contribution, then all that's needed is to
 include the line in your commit or pull request comment::
 
     Signed-off-by: Your Name <[email protected]>
-
-...using your real name; unfortunately pseudonyms and anonymous contributions
-can't be accepted. Git makes this trivial - just use the -s flag when you do
-``git commit``, having first set ``user.name`` and ``user.email`` git configs
-(which you should have done anyway :)
+
+We accept contributions under a legally identifiable name, such as
+your name on government documentation or common-law names (names
+claimed by legitimate usage or repute). Unfortunately, we cannot
+accept anonymous contributions at this time.
+
+Git allows you to add this signoff automatically when using the ``-s``
+flag to ``git commit``, which uses the name and email set in your
+``user.name`` and ``user.email`` git configs.
 
 Conclusion
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