I am glad to see you bringing this topic up. Recently additional censorship mechanisms have come to my attention that you did not address in the OP. Steemit and Steempeak, at least, are censoring certain accounts so completely that votes those accounts cast are 'mystery votes' which the front ends do not ascribe to the voting account. I am assured by @a-non-e-moose that the blockchain still registers the votes, and egregious spam comments are indeed conserved on Steem itself, but these front ends completely censor the post, comments, and even the source of votes cast by these accounts.

Have a look at this post and you will see what I have learned regarding this practice.

It is blatant, unmitigated censorship - but only of the front ends. Steem, the blockchain, is itself not censoring these posts, comments, or votes. I may have poorly linked the post above, but scrolling up to the original post will reveal the entirety of the matter. I strongly disagree with this practice, and believe that empowering individual accounts to block such spam on their blogs is a vastly preferable solution to allowing front ends to prevent individuals from making those decisions for themselves.

Thanks!