I think the positive reactions are probably mostly a case of guessing the teacher's password. Perhaps the teacher conveyed a positive impression beforehand, but the default password guessing behavior would probably be to guess "teacher wants us to write about this appreciatively" regardless of whether he said anything additional about the site -- that would be expected for a community blog devoted to refining the art of {rationality, wisdom, justice, aesthetics, ...}.
After having read the comments, I can definitely sympathize with the students. It brought back memories of when I was in the same position in history or English class when we had to read something and write our reaction to it but with little clear direction about what was expected of us or how the teacher would grade, and not really caring about the subject matter. I know the process that produced the comments, and I would probably write the same things in their position, but not out of deficient intelligence or writing skill -- rather, because I don't s...
Link.
Given the positive reactions, I think the professor seeded them with a positive impression of the site's content.