Would you care to be explicit about the censorship to which you refer? Can you give specific examples and back it up with concrete data? Personally, I'm not sure what you might be thinking of ...
Most stories die because they get flagged by users. Duplicates, things that are boring, plagiarized, etc. Interesting links almost always get submitted multiple times, so it isn't a huge loss to the site if one of them dies unfairly.
Stories can get demoted of the front page by triggering "flame war" like behavior. This is fine IMO because it keeps otherwise reasonable people from feeding the trolls, while the trolls are likely to keep trolling each other (and burning karma) out of public view. The moderator does review at least some of these and fixes the demotion if necessary.
Stories can be manually demoted if deemed "not interesting" by the site admins. This could be problematic, but from what I've seen it is used rarely and reasonably.
There is a proposed thing called "pending comments" which I'm not a huge fan of. I think the tools we have today are good enough and that it unnecessarily burdens the new user experience. IMO people who post low quality comments already get punished by the community at a sufficient level that they either improve or leave. Note that this is theoretical since we haven't seen what this feature looks like in practice.
I do wish there was some more concrete guidance on how the moderation tools were meant to be used (flagging stories specifically) but in those cases you just use the tools cautiously until you have a better understanding of community norms.
Note that I have no affiliation with Hacker News or YCombinator and this solely represents my personal opinions.
In particular, look at these comments:
https://news.ycombinator.com/item?id=7826954
https://news.ycombinator.com/item?id=7826943
In both cases the posts were explicitly unkilled - the opposite of censorship.
I'm going off-line now, but I'll see any replies in the morning. To answer your question, my feeling is that, in general and overall, the actions of the moderators are having a positive effect in the quality both of submissions and discussions.