Keep your staff notes separate from the customer correspondence: (My grandfather actually got the bedbug letter in the late 1920s, after being bitten on a Pullman carriage - though not the attached note.)
“The Bedbug Letter” (from http://www.snopes.com/business/consumer/bedbug.asp).
A wealthy gentleman was badly bitten by bugs while riding on a certain railway line. Arriving at his destination, he wrote the company an indignant letter and received a prompt reply. It was, said the letter, the first complaint the company had ever had of this nature. Inquiry had failed to reveal any explanation for this unprecedented occurrence. Nevertheless, a number of new precautions were being taken to make absolutely certain such an unfortunate incident never happened again. The letter was signed by a high official of the railway.The gentleman was well satisfied with this reply and was returning it to the envelope when a slip of paper fell out onto the floor. The hastily scribbled note on it read: "Send this guy the bug letter."
