Yes, it was bound to "Jump". I don't recall setting that, because Backspace has been doing the same thing since I first launched the program.
Having un-bound it, it appears to be clearing binds both for keyboard and controller mappings. Perhaps it would be a good idea to prevent Backspace from ever being bound to an action, as you said.
EDIT: Also, having un-bound Backspace, now it appears that the demo is recognizing the X button on my knock-off Saturn controller as "Select". I can guarantee that this was not the case when I first launched the program.