The following example is indeed not perfect.  It's single parameter
should be named "that" and not "other" because it is referred to as
"that" in most of the body.

// A better definition, but still not perfect
override def equals(other: Any) = other match {
  case that: Point => ...
}

Listing 30.2
------------------
case that: ColoredPoint =>
  (that canEqual this) && 
   super.equals(that) && ...
------------------

The "that canEqual this" part is redundant, because the same check is
done inside "super.equals(that)" already.

The sentence "The only exception to this requirement is for final classes
that redefine the equals method inherited from AnyRef." seems
contradictory to the initial sentence of rule #1. 

Sorry if I have misunderstood the rule.