Not "any string at all". Do it to a maximal-entropy string (e.g., a genuinely random one) and you won't see an increase.
You're using "information" in the colloquial sense, where random junk is not information. Norvig is using it in the information-theoretic sense, where random junk has more information than anything else of the same length. The information-theoretic sense is not "nonsense"; it's just not the same as the colloquial one.
(Motivation for the terminology: the "information" in a string is the minimal number of bits -- i.e., the minimal amount of information -- it takes you to tell me what the string is.)
You're using "information" in the colloquial sense, where random junk is not information. Norvig is using it in the information-theoretic sense, where random junk has more information than anything else of the same length. The information-theoretic sense is not "nonsense"; it's just not the same as the colloquial one.
(Motivation for the terminology: the "information" in a string is the minimal number of bits -- i.e., the minimal amount of information -- it takes you to tell me what the string is.)