Everything is on the blockchain. Steemit.com is just 1 of many interfaces to that blockchain. Steemit can do whatever they want with how they display the data but it will always be completely viewable in its entirety directly from the blockchain or from some other site that choose to display things differently.
RE: Steemit removed the ability to see who downvoted posts, it seems that this platform is not moving in the direction of decentralization.