Finished, the post is here: https://www.lesswrong.com/posts/PyChB935jjtmL5fbo/time-and-energy-costs-to-erase-a-bit
Summary of the conclusions is that energy on the order of kT should work fine for erasing a bit with high reliability, and the ~50kT claimed by Jacob is not a fully universal limit.
Finished, the post is here: https://www.lesswrong.com/posts/PyChB935jjtmL5fbo/time-and-energy-costs-to-erase-a-bit
Summary of the conclusions is that energy on the order of kT should work fine for erasing a bit with high reliability, and the ~50kT claimed by Jacob is not a fully universal limit.