I help moderate a mid-size subreddit (100,000-500,000 subscribers) and we're completely overrun by low quality content.
We tried adding new rules, silently removing/banning offending users, and making repeat announcements, but it seems like it's too little too late. A rehashed joke post can easily receive 100+ points in an hour while a good post may receive, at most, 20 points in the same time.
Don't make voting visible and don't show people their points. You still need voting so popular topics bubble to the top. You still maybe need user points so users who post bad content get bad scores? (maybe you don't need this).
What you don't need is for any of it to be visible. User's seeing their points go up is a gamification technique that pushes their (and my) button. "Oh! I just got 150pts!" feels so good so I'm compelled to try to get more points.
I notice my point total here on HN. Every time I see it go up I'm conscious of a little pleasure bump I get "oh, some people agreed with me or thought my post was useful!". I've thought about writing a browser extension to hide it from myself. Mostly the only thing I want to know is if I got replies.
It changed the sub significantly. Some people liked the more serious tone, some people felt like the fun had been sucked out. At the end of the day, you can't please everyone.