Sane humans would call these invalid tests, but Andrew McNamara pointed out

that given the inputs in these tests Excel does indeed produce the output
these tests expect.  Document that for future confused folks.

Lib/test/test_csv.py

@@ -484,12 +484,16 @@ class TestDialectExcel(TestCsvBase):
         self.readerAssertEqual('a"b"c', [['a"b"c']])
 
     def test_quotes_and_more(self):
+        # Excel would never write a field containing '"a"b', but when
+        # reading one, it will return 'ab'.
         self.readerAssertEqual('"a"b', [['ab']])
 
     def test_lone_quote(self):
         self.readerAssertEqual('a"b', [['a"b']])
 
     def test_quote_and_quote(self):
+        # Excel would never write a field containing '"a" "b"', but when
+        # reading one, it will return 'a "b"'.
         self.readerAssertEqual('"a" "b"', [['a "b"']])
 
     def test_space_and_quote(self):