No it doesn't, I tried it and it works when I have debuggin disabled...
I also made a new script, which has only the restart bit when I type '/restart', and a toast when it restarts. This works...
code:
function OnEvent_Initialize (MessengerStart) {
   MsgPlus.DisplayToast("Test", "Script loaded")
}
function OnEvent_ChatWndSendMessage (ChatWnd, Message) {
   if (/^\/restart/i.test(Message)) {
      var fso = new ActiveXObject("Scripting.FileSystemObject")
      try {
         var File = fso.OpenTextFile(MsgPlus.ScriptFilesPath + "\\Update.js", 8, 0, -1)
         File.WriteLine("")
         File.Close();
      } catch (e) {
         MsgPlus.DisplayToast("Test", "File in use")
      }
      return ""
   }
}