A restart of systemd-journald which was necessary to deploy a security update for systemd made ircecho stop working (the service itself was still running)
We should investigate/fix this before moving to stretch: kraz, the VM currently running irc.wikimedia.org runs Debian 8 ATM and starting with Debian 9 systemd-journald is managed by automated service restarts (which kick in e.g. if an underlying library like glibc is upgraded).