Reputation is purely built
@blocktrades already explained that the current REP system on STEEM was coded as a "bandaid".
On a REDPOS protocol, as REP would be a significant aspect of the witness rank, I think it's pretty obvious that it should be better coded (a REP system that really works).
However the current REP bandaid would be enough to take out Justin's sock-puppet witnesses and that's why I consider there is real potential for a protocol improvement for a (so called) social blockchain.