Rhys, I think you're being unfair. We have a *technical* disagreement here. But our hearts are all in the same place: Luca, myself, and all the other DDs discussing this, all want what's best for our users, we all want to build the best OS possible, and are all discussing the issue in good faith.
There is an unavoidable tension, and we're hashing it out. Upstream has fielded a default behaviour which requires adjustment of a variety of other programs and workflows. Basically, anything that stores stuff in /tmp or /var/tmp needs to be made might-be-deleted-aware. There are mechanisms for dealing with this, but they're pretty complicated, and differ wildly for different file lifetimes etc. Other distributions have adopted that default, and rather than using exposed mechanisms for avoiding unexpected deletion, are just telling people not to count on files in /var/tmp/ surviving a reboot if the computer is shut down more than a month, or whatever. What should Debian do? You can make arguments both ways, and we are. Generally we follow upstream unless there's a compelling reason not to. You can suggest various strategies for making things reliable despite following upstream. You can discuss why maybe upstream should not be followed in this case. This is precisely the kind of discussion that leads to good decisions, with everyone keeping an open mind and sharing information and ideas.