I meant more like trust in communities and admins. If you can trust that the admins and moderators will do their task well, you shouldn't have to worry about keeping track of these users yourself.

Karma in the style of reddit is not and has never been a great proxy for whether a user is "good" or "bad". It mostly just says something about how active a user is and for how long they have been active, and how much they agree with the hivemind. Agreeing with the hivemind is not necessarily the criteria you want, as that just leads to more echo chamber situations.