@Kaz, Thank you for introducing the #: notation and the circle notation. As you said, gensym can be omitted in many macros, without creating many different uninterned symbols that share the same names.

In cotontrast, in the sortf macro, different #:NEW1 symbols should be used, and get-setf-expansion already makes a new uninterned #:NEW1 whenever it's used. In sortf, the number of #:NEW1 symbols is proportional to the number of arguments that are passed to sortf. Therefore, sortf cannot use the fixed number of symbols that can be generated by the #: notation.