I managed now to implement a basic Karma system, just like reddit. You can give 0,1,-1 karma to a user as long as he is settler and more than 10 days registered on the website. To find out the commands please go to the brand new Karma page on the website.
For those who are wondering about the subjects of the last 3 posts please see this here.
Further, as you can see down here on the left, there is also a new karma-like system on the website. I dumped the facebook/twitter thing and opted for a site-specific feature so people can leave their opinion about stuff w/o having to link their facebook account to the site and leave a simple opinion. So click away and give karma as you like!