-;;; Return T iff CONSTANT has not already been dumped. It's been
-;;; dumped if it's in the EQ table.
+;;; Return T iff CONSTANT has already been dumped. It's been dumped if
+;;; it's in the EQ table.
+;;;
+;;; Note: historically (1) the above comment was "T iff ... has not been dumped",
+;;; (2) the test was was also true if the constant had been validated / was in
+;;; the valid objects table. This led to substructures occasionally skipping the
+;;; validation, and hence failing the "must have been validated" test.