Have Superman fly around the world and reverse its rotation.
There is no undo as far as I know. For lengthy posts, I bring up a mini-text editor (such as Notepad on Macintosh or Wordpad on MS Windows), type my reply in there, and do a copy and paste.
La franchise ne consiste pas à dire tout ce que l’on pense, mais à penser tout ce que l’on dit.
H. de Livry