DOCS-64 minor changes to note

source/reference/operator/rename.txt

@@ -171,17 +171,22 @@ $rename
         Before version 2.2, when renaming multiple fields and only some (but
         not all) old field names refer to non-existing fields:
 
-        - **if** no field exists with the new field name, the
-          :operator:`$rename` operator does nothing.
+        - For the fields with the old names that do exist, the
+          :operator:`$rename` operator renames these fields to the
+          specified new field names.
+
+        - For the fields with the old names that do **not** exist:
+
+          - **if** no field exists with the new field name, the
+            :operator:`$rename` operator does nothing.
 
-        - **if** fields already exist with the new field names, the
-          :operator:`$rename` operator drops these fields.
+          - **if** fields already exist with the new field names, the
+            :operator:`$rename` operator drops these fields.
 
-        Consider the following operation that renames both the
-        field ``mobile``, which exists, the  field ``wife``, which
-        does not exist. The operation will set the 
-        field named ``wife`` ``alias``, which is the name of an
-        existing field: 
+        Consider the following operation that renames both the field
+        ``mobile``, which exists, and the field ``wife``, which does
+        not exist. The operation tries to set the field named ``wife``
+        to ``alias``, which is the name of an existing field:
 
         .. code-block:: javascript