Testing equality
 aNumber = (aNumber + 0 i)
will answer false...

Testing equality
 (aNumber + 0 i) = aNumber
will answer true...

(1 + 0 i) = 1.
1 = (1 + 0 i).

This is due to premature test
 isNumber ifFalse [^false].

Obviously, Complex cannot answer true to isNumber because most senders of this 
message will trust faithfully isKindOf: Number, and Complex is not in this 
hierarchy.

The test should be some sort of
 isArithmeticValue ifFalse: [^false]
and Complex Quaternion and other arithmetic classes extending numbers should 
answer true to isArithmeticValue.

This is another clue that VW ArithmeticValue superclass of Number make sense.
And another clue that Complex (ComplexNumber please) are not much used.