Ummm ... don't we strongly encourage all package maintainers to read d-d-a? If not, we should. It is very low traffic and sometimes important.
Remember the removal mails also end up in the history on packages.qa.debian.org which afaict is the main point of reference for those who are trying to find out what is going on with a package.Sure: “All developers are expected to be subscribed to this list.” [0], but Oliver was referring to “users”. On the other hand, his example mail (To: duplicity@packages.debian.org) is obviously sent to developers, so I'd guess no harm is done for our users.
Not everyone who has an interest in why the package they rely on is suddenly no longer in testing is a dd or a package maintainer.