Touch have karma system to separate users of the sate to different groups. Groups are set in Touch global configuration. Activity of the users may (or should) affect their karma and karma of other users. You may increase or decrease user karma through Touch API.

Here is the example

$API = JPATH_ROOT.DS.'components'.DS.'com_community'.DS.'api.php';
if(file_exists($API))
{
    require_once $API;
    JSCommunityApi::increaseKarma($user_id, $amount);
}

Amount may be negative if you want to decrease user Karma.

As an idea it is good to use parameters how many increase of decrease on what action. Allow your customers chose. Also it is nice idea to increase/decrease karma not only to user who acts, but to user affected. For example if someone rate article, one who rate get 2 points and one whose article rated 1-5 depending on rating given.