You can set clipboard.autocopy to false in about:config to disable this. It breaks the example, at least.
EDIT: I thought the behavior was preserved for textareas, as the comment box here still copied on select. But it suddenly disabled it here too. Restarting the browser is probably a safe bet :)
EDIT: I thought the behavior was preserved for textareas, as the comment box here still copied on select. But it suddenly disabled it here too. Restarting the browser is probably a safe bet :)