If the play/stop button is selected and ctrl + space (default shortcut) is pressed, first Wikispeech.playOrStop() is triggered, then the button click event fires, triggering playOnStop() again. The result is that the player starts playing after stopping and stops after starting.
The behaviour may changed, if for example a media player GUI is used.
If not, stopping the event from bubbling should solve this: http://api.jquery.com/event.stopPropagation/. event.preventDefault() is probably what we want.