This is a linkpost for http://curi.us/2065-open-letter-to-machine-intelligence-research-institute
I didn't correspond with David Deutsch in an "informal way" as you mean it. For example, I was the most important editor of BoI (other than DD ofc).
You don't seem to be a formal coauthor of the book, so your relationship is informal in a way that a Phd supervision isn't. The book also doesn't list you as editor but under "friends or colleagues" while he does mention that he does have a relationship with someone he calls copy-editor.