I had the same worry/question when I first found LW. After meeting with all the "important" people (Anna, Luke, Eliezer...) in person, I can confidently say: no, nobody is carrying around a sheet of paper and doing actual Bayesian updating. However, most people in these circles notice when they are surprised/confused, act on that feeling, and if they were wrong, then they update their believes, followed soon by their actions. This could happen from one big surprise or many small ones. So there is a very intuitive sort of Bayesian updating going on.