In an informal seminar in the morning, Rashid Sunyaev (MPA) finally explained to me clearly why the CMB does not show Lyman, Balmer, Paschen, and so on recombination lines: The answer is that the baryon-to-photon ratio is so enormous that recombination contributes only a minute fraction of all photons. He showed nonetheless that it might be visible in the future by proposed PIXIE.
Prior to that talk I gave the last of our stats school lectures, this one on machine learning. I described some of the popular goals and methods in machine learning and connected them to physical science problems. I gave strong advice, which was mainly to avoid large classes of algorithms. In the afternoon, Shirley Ho (CMU) told us about a use of machine learning to take a few good simulations and lots of bad ones and build lots of (pretty) good ones at low cost.