I like that idea. I've changed to using shift for deletion. I've also enabled deleting on both mouse clicks and movement, so you can hold down shift and wiggle the mouse around like an eraser. This makes it much easier to delete lines.
Thanks! I like that you can delete on mouse movement -- I think it's actually better and more intuitive than my original suggestion.
It seems that vertical lines can only be erased when mouse moves vertically or almost vertically while holding shift.