Here is what Reddit has to say about Karma:

The formula for karma is constantly evolving (or, being intelligently redesigned, if you’d prefer). Presently, the easiest (and most effective) way to gain karma is by making good submissions: items that other people want to read and will subsequently become popular. Those redditors who best understand what people want to be reading about will be the best rewarded.

So, it looks like the formula is probably unknown. I believe that a user gains or loses karma based on the moderation on submitted links and comments. Unlike slashdot, each vote weighs equally, even though the karma of the voter may vary.

I think Slashdot does so much better of a job with moderation due to a few reasons:

1. Only regular users get moderation points
2. Moderation points aren’t unlimited; they only get 5 each time
3. Poor comments result in penalties to a commenter’s karma rating
4. The score, and thus the visibility, of each comment is also affected by the commenter’s karma rating
5. There are meta-moderators, so poor moderation also results in karma penalties
6. Slashdot users are just geekier.

I looked at the thread on .999… vs. 1 on Reddit, and I have to agree with you, Matt. The comments, while not as interesting or informative as Slashdot comments often are, weren’t nearly as bad as the one’s on Digg. I have no idea why, though. Reddit also offers unlimited moderation points, and offers them to anybody who signs up. How does karma work on Reddit? Do you know?

“ccanni1028 by ccanni1028 15 hours ago
Using the same type of logic as what is in the arcle, there is also proof that 1=2!!!

1/0=0
2/0=0
0=0 so 1=2″

HAHAHA!!! Oh my!
I think the main problem with doubters is that they don’t realize that even integers have infinite precision, ie 1 = 1.000… . Infinite precision does not mean not-a-number. *sigh*

degustibus -83 points 21 hours ago*

No, it doesn’t equal one. Think of the number line. Infitessimally to the left of one is .999 repeating. One is to the right of this value. 1/infinitiy is not the exact same as zero. I’m using the word equal in the sense of identical. I know that axiomatically one derives .999r = 1, but to say that a fraction of one is one clearly makes no sense. You learned something in 15 minutes. You didn’t prove it and you certainly don’t know it. There is a difference. Why do we have .999r and 1? What is it that .999r represents? Yes, it is a tedious argument that has been beaten to glue. The limit of .999r is one, but the limit is the asymptote, no? The value ever approached but never reached.

Overall, in glancing through the comments it seemed that the Reddit crowd was fairly good at moderating the idiots way down. I’m wondering whether the Reddit crowd is a little smarter than the Digg crowd. Or maybe Reddit has a better moderation system? Maybe Reddit is new enough that the layfolk haven’t found it yet.