If this variable is present, then for some reason the complete ftplugin file is sourced everytime a Vimwiki buffer is entered, even if the buffer has been entered before, i.e. the guard b:did_ftplugin has no effect. (See /usr/share/vimXX/ftplugin.vim) Deleting these lines. I don't think undoing the settings is a common use case, anyway.