The bottle you regret buying teaches you more than your favorites

I build a fragrance app, so I spend a lot of time in how people describe what they own. One pattern keeps surprising me. The bottle someone bought and never reaches for predicts their taste better than the ones they love. A favorite tells you what you aspire to. A regret tells you what you actually are, and that turns out to be the more useful signal.

So a question for the room, in two parts. If you have built recommendation systems in other categories, do you find negative signal beats positive signal for figuring out a person? And a question for the fragrance people here. What bottle do you regret buying the most, and what did it teach you about your taste?