everyone makes good points;
Of course we have to remember that this MMM's blog. He busted his ass to build it so it does not matter what anyone else thinks about whether blog comments should be delete or not. He is the final decision maker on the issue. Heck he could shut this whole thing down tomorrow and there is nothing me or you could do about it.
That being said, the problem with the selectively censorship, is that casts a glimpse of doubt into the validity of the positive feedback shown on the main blog's pages. The fact that we know any least some comments have been removed, yet we don't know what those comments said, means that there is not full disclosure. Thus, how can one truly trust that the positive comments posted really are an accurate public measure of opinions expressed?
How do we know whether legitimate criticism has been blocked or not? I think this what is prompted, in part, a discussion on reddit recently criticizing MMM's moderation. I like this blog and however this comment moderation might a source as to why it does not get more credit from the general public. I don't know whether allowing every comment through is best solution though, however I think this reasoning explains why some people doubt the feedback as being so positive.