Thread:Topdarlingwh/@comment-8161155-20150927051333/@comment-10771297-20150927060454

"This is a production error." Is not an independent clause. "An independent clause (or main clause) is a clause that can stand by itself as a simple sentence. An independent clause contains a subject and a predicate; it makes sense by itself and therefore expresses a complete thought."

There's no subject in that phrase. "This" is replacing the whole sentence of, "The symbol on the cryptogram spell "FOOJISH..."