But did he say "please don't tell anybody who I am or where I teach?" This is completely orthogonal to the question of preventing comments from LWers, aggrieved or otherwise.
I wasn't interested in writing a comment on the blog (except possibly to ask where the course was -- and I might very well have done so, since Luke's post does not contain any instruction to the contrary! So if info was somehow being hidden with the goal of preventing comments, it would have directly backfired.).
I was able to figure out what university the course is from information in the comments with high probability and an trivial amount of googling but I'm not sure if it would be socially appropriate to share the results.
Link.
Given the positive reactions, I think the professor seeded them with a positive impression of the site's content.