User blog comment:Dopp/Technical Update: November 29, 2011/@comment-1331296-20111202182242/@comment-1997905-20111202182705

That's a different problem - if you click the edit button twice, depending upon the status of your first request to the server, it's possible to edit conflict yourself. Occasionally, the button will register two clicks even if you only think you clicked it once. Changing your signature from tildes to wikitext doesn't register as an edit, it's part of the parser.