Changing or obscuring content is censorship. There is no definition of censorship in any widely accepted source that defines censorship only as complete elimination of content. Even before blockchains, such total elimination was almost impossible after the advent of the printing press. Access to the blockchain data is limited for most people to that revealed by front ends, as few folks can code their own. Censoring the front ends is effective censorship. Worse than downvoting as censorship is Steemit lately censoring creators itself, which prevents individuals from controlling their own feeds of information. See Github's irredeemable list for specific accounts so censored.

For examples of creators being crushed by flagging, have a look at @skeptic's account.