Fun read. Topic modeling can be fascinating to work with. Curious how they measured performance of their model, and whether they found a "best" number of topic

Fun read. Topic modeling can be fascinating to work with. Curious how they measured performance of their model, and whether they found a "best" number of topics for LDA where their model stopped getting much benefit by having more topics. I'd imagine increased number of topics would have some interesting side effects where it would create too narrow of recommendations.