revert part of cefe4f38fa0e, as agreed with Éric

Doc/glossary.rst

@@ -519,11 +519,10 @@ Glossary
    nested scope
       The ability to refer to a variable in an enclosing definition.  For
       instance, a function defined inside another function can refer to
-      variables in the outer function.  Note that nested scopes by default work
-      only for reference and not for assignment.  Local variables both read and
-      write in the innermost scope.  Likewise, global variables read and write
-      to the global namespace.  The :keyword:`nonlocal` allows writing to outer
-      scopes.
+      variables in the outer function.  Note that nested scopes work only for
+      reference and not for assignment which will always write to the innermost
+      scope.  In contrast, local variables both read and write in the innermost
+      scope.  Likewise, global variables read and write to the global namespace.
 
    new-style class
       Any class which inherits from :class:`object`.  This includes all built-in