@Kees: I can think of a possible reason why initscripts.postinst copies the /etc/motd to /etc/motd.tail. Consider someone using their own custom motd in /etc/motd. Upgrading would cause initscripts to clobber this. The postinst keeps this from happening by preserving it as /etc/motd.tail. Perhaps it just needs to be smarter about only doing this if the file doesn't seem to be a stock motd?
@Kees: I can think of a possible reason why initscripts. postinst copies the /etc/motd to /etc/motd.tail. Consider someone using their own custom motd in /etc/motd. Upgrading would cause initscripts to clobber this. The postinst keeps this from happening by preserving it as /etc/motd.tail. Perhaps it just needs to be smarter about only doing this if the file doesn't seem to be a stock motd?