Votes and karma. The concept of karma isn't bad but Reddit's implementation is bad. HN has a similar problem. There's only up and down votes with no context.
Why was a post upvoted or downvoted? Did people find it funny or informative? Did it correct the original link or a parent post? No fucking clue. Just scalar value that goes up and down. Then you get bad proxies for context with vote ratios (controversial etc).
Slashdot's voting system isn't perfect but much better. Instead of some scalar value a post is moderated with some sort of context (Interesting, Informative, etc). Voting is also distributed among users and limited. If you get moderator points you're limited in how many you get and you can't post to a thread you've moderated. Meta moderation also helps to correct for overzealous/reactionary moderation.
The context is useful because you get an idea of why something was moderated as it was. The limited number and random distribution of moderation points helps inspire actual moderation. You either downvote obviously trolling/bad faith posts or upvote actually constructive posts. No one wastes their mod points on memes and "me too" posts. Drive by memes and short knee jerk replies just wallow in the Score: 1 area most users quickly learn to filter out. They're not punished but also not rewarded.
Giving everyone unlimited mod points devolves a site into gaming karma. Trolls enjoy seeing how low their karma can get while karma whores will post whatever gets upvotes rather than something constructive. Karma is a bad proxy for constructive contributions to the community.