When an ongoing dialog of comments and replies is attempted, the previous replies are lost when sending from 2013 to 2003. When the recipient replies to me, only his most recent comment appears in the balloon. He is unable to see my previous reply and the thread of the dialog is lost.

This is a very serious problem in my work as a book editor. None of my clients have Word 2013. Some have 2007 to 2010, but MANY have 1997-2003.