Its difficult to be the judge on this stuff since it is so subjective. We're not technically deleting anything. And you are always given the option of clicking the threshold control over to '-1' and reading everything uncut, so I really have a hard time saying this truly is censorship. But if you really want to call it that, I can't really argue. We're trying to make as many people happy as possible here- if you don't like something, you can probably change it in the user preferences to more suit your tastes anyway.
Good Comments are insightful.
You read them and are better off having read them. They add new information to a discussion. They are clear, hopefully well written, or maybe amusing. These are the gems we're looking for, and they deserve to be promoted. Average Comments might be slightly offtopic, but still might be worth reading.