Starting with 0.8.10-rc5 (released 5 minutes ago) and irssi-cvs since few weeks ago, packaged irssi-charconv and irssi-recode are obsolete. This same function is now integrated within Irssi core itself. The old ebuilds should probably be updated so that they cannot be installed together with new Irssi versions. Note: this new recode completely solves all UTF-8 problems, in addition to plenty of other charset incompatibilities.
I added 0.8.10_rc5 to portage and made it block net-irc/irssi-charconv and net-irc/irssi-recode. And also the other way round.