@ geeman:
I've seen that implemented for a news-comment system on a website I frequent quite often. It was removed after a few weeks.
The simple matter of fact is that in the end, it's people that hit the buttons. And despite a few exceptions, people generally do not understand how such a system is supposed to be operated, or even worse they misuse it deliberately. So whichever way you twist and turn it, the overall result of rep and shown/hidden posts will not represent the actual situation of good and bad content, rather than simply reflect the opinion of Joe Average. May it be public or hidden, with or without comments, points and power, as long as people don't get it, it becomes moot sooner or later. The problem is not in the system, it's the people that use it.