Ask HN: Most advanced online courses (A/B, SM-2, Pricing)?

What is the most advanced online course platform for learning? - None seem to use A/B testing with users? - None seem to use SM-2 learning for reviewing? https://www.supermemo.com/en/archives1990-2015/english/ol/sm2 - AI which learns how you learn and modifies teaching style? - Few seem to assign you a mentor (which could be an old student). A few seem innovative: - Duolingo on their pricing - Lingq on their mixture of reading, and audio learning - MOOCs on their use of student mentor - correction groups - udemy in that anyone can become a teacher What is the most advanced course you have taken? Is anyone pushing the boundaries on teaching tech?