Without rep moderation, that is just simply untrue. For instance, D3v was the first person to reach 3 bars. By cheating. That doesn't make him look credible at all.

If rep were made public, and were moderated, it WOULD serve a bit of a purpose, even without having incentives for having higher rep. Either way, if someone doesn't give a shit about their rep, then negatively repping them won't matter.

This is my point. If it's tied into a shop system of sorts, you essentially MAKE people want positive rep, and encourage people to not be asshats, so they don't get negative rep.