I left an old netbook to do an ”apt-get -y dist-upgrade” overnight, and when I returned to it the next morning, the upgrades were unfinished because libc upgrade was waiting for me to respond to ”Restart services during package upgrades without asking?”

It looks like the question is prioritized depending on whether the upgrade is done on desktop or not, and if it’s not, the priority is set critical. According to documentation [1], critical is for ”Items that will probably break the system without user intervention.” I don’t think restart-without-asking satisfies that condition.

* [1] http://www.debian.org/doc/packaging-manuals/debconf_specification.html#AEN101