Are Delighters equivalent to Gold Plating? Is there a link / similarity between the delighters mentioned in Kano model and gold plating? Do both these terms define the same concept? Can a delighter be a cause for a project failure?

These are two judgement labels applied to the exact same behavior, based on the outcome. If you get it right, the customer is delighted. If you get it wrong, you gold plated and the customer is upset. I think the concept of gold plating in project management, and the teachings around the concept of avoidance, is based on the thought that the risk of getting it wrong is much greater than the opportunity of getting it right, and the impact of getting wrong--increased sunk costs, rework--is much greater than the customer satisfaction of getting it right.