Last week, Jono Bacon published a YouTube video discussing the karma system used by Reddit. It’s worth 28 minutes of your time if you’re thinking about a reputation system for your community. I don’t have any disagreements, but there are a few “yes, and”s that popped up as I watched it.
What’s karma for?
A fundamental problem with karma is that it applies to posts/comments, not to accounts. Yes, Reddit displays a net karma score on account profiles, but it doesn’t do anything with it. A large number of upvotes will move a post or comment toward the top. A large number of downvotes will hide a comment behind a “wow, do you really want to see this crap?” (my words) link. But apart from removing a posting frequency speedbump for new accounts, the account’s karma doesn’t actually mean much.
Karma is non-specific
Another big issue with Reddit karma is that it’s the same across the entire site. Jono talked about using karma as a metric of credibility. If you narrowly define “credibility” as “knows what the community likes”, then that works. But I might earn a bazillion points for my insightful open source posts. When I go to post in an small engine repair subreddit, my karma comes along with me.
Just because I can successfully participate in one subreddit, that doesn’t mean I can in another. And it’s certainly not a measure of expertise on a topic. Jono alludes to this by talking about how karma doesn’t distinguish between funny and helpful, for example.
You can’t buy karma. That’s one of the benefits of Reddit karma. But you can buy accounts to apply karma. Whether you pay money to a bot farm or just wield your influence on another platform, you can drive upvotes or downvotes to an account of your choosing. Since karma is mostly meaningless at the account level, the direct harm of this is fairly small. But brigading is always a concern in online communities.
Okay, so then what?
Reddit karma has its downsides. But it is very simple, which is a huge benefit. I tend to favor the more account-centric systems like Discourse trust levels and StackExchange reputation. Sites like ArsTechnica have an up/down vote systems with an optional tag to explain why you’re giving the vote. If Reddit’s karma was per-subreddit, it would be more useful as a measure of credibility.