Comment 13 for bug 72054

The zsh manual says the viins mode is automatically turned on if the EDITOR environment variable contains anything linke 'vi'.
http://zsh.sourceforge.net/Doc/Release/zsh_17.html#SEC92

The additional ubuntu keybindings cause a lot of trouble if someone exports EDITOR=vim in .zshrc and starts an other zsh instance via sudo -s oder screen. The new instance starts with viins mode and the keybindings in /etc/zsh/zshrc are activated.

This doesn't affect a normal login shells since the environment most likely doesn't have the EDITOR variable set.