*   <li>Next, if only one {@code Bar} is null, that null value is treated as <i>lesser</i>
 *   <li>Finally, natural ordering is used (i.e. the result of {@code Bar.compareTo(Bar)} is
 *       returned)
 * </ol>
 *
 * <p>Alas, {@link #reverse} is a little different. As you read backwards through a chain and
 * encounter a call to {@code reverse}, continue working backwards until a result is determined, and
 * then reverse that result.
 *