Version: (using KDE Devel) Installed from: Compiled sources currently, it seems like the Nickname list cannot have a different encoding. When entering channels that have clients with non-English nicknames, there names do not get interpretted correctly. I think nicknames should correspond to the channel encoding. And although I have not yet tested this, it might also be a good idea for your own nickname to be sent to the server encoded in the locale that you wish.
i can confirm it. Nickname list seems to have a different encoding from main chat.