“Duolingo does it” is one of the easiest ways to make a weak product decision sound researched. Someone suggests a feature. Someone else points to Duolingo. Now the idea feels validated. I saw this happen during a product review. The reference gave us a useful example of how an interaction could work. The visible feature was only the surface. Behind it were assumptions about the audience, the behavior being encouraged, how often someone uses the product, and what the product is trying to teach. Those assumptions belonged to Duolingo. Copying the feature would have brought them into a completely different product without anyone discussing whether they fit. In that review, we kept Duolingo as the reference and went back to our own users before deciding what to build.