Many conditions defined there have almost the same reports that could altogether be simplified to (format stream "A condition of type ~S was signaled." (type-of condition)). Perhaps it would be good to define this report as a method on condition and let all other conditions inherit this default reporter?
https://github.com/robert-strandh/SICL/blob/e19613c61d8797a9ea586e3c513efdaeb0860d68/Code/Conditions/conditions.lisp#L23-L27
Many conditions defined there have almost the same reports that could altogether be simplified to
(format stream "A condition of type ~S was signaled." (type-of condition)). Perhaps it would be good to define this report as a method onconditionand let all other conditions inherit this default reporter?