The point of the article, perhaps not stressed enough, is that there are stable systems that can be very difficult to control. Zeros in the right half-plane don

The point of the article, perhaps not stressed enough, is that there are stable systems that can be very difficult to control. Zeros in the right half-plane don't indicate instability. They indicate nulls in the transfer function for unbounded inputs. Poles in the right half-plane indicate instability. Zeros in the right half-plane indicate something a little more subtle. I believe the article is about the latter.