# File lib/sup/modes/thread-index-mode.rb, line 700
  def add_or_unhide m
    @ts_mutex.synchronize do
      if (is_relevant?(m) || @ts.is_relevant?(m)) && !@ts.contains?(m)
        @ts.load_thread_for_message m, @load_thread_opts
      end

      @hidden_threads.delete @ts.thread_for(m)
    end

    update
  end