Censorship implies that information has been invisibly removed by some absolute authority. Whereas here we're talking about empowering users to filter out the stuff on their terms - i.e. subjective/relative reputation. It's possible that a server admin might apply unilateral filters, but a) the user would be able to visualise those (assuming the server admin doesn't maliciously withhold that info), b) the user can switch to another server with different filtering rules. So, I definitely wouldn't characterise it censorship (although I can see why many have a kneejerk reaction of "ooh, this sounds a lot like censorship").