I think you are referring here to stick force stability, not aeroplane stability.
Negative .. refer, for instance, to
FAR25.173 and
FAR 25.175.
All the usual stories about balls in teacups and such are fine but, at the end of the day, it comes back to off trim speed stick forces. Indeed, I always find the ball and teacup confusing .. unless we are talking about HOLDING the ball somewheres up the side of the teacup ... but that might just be me, I guess.