It could be reddit's motto as well. I've not found a post >100 upvotes that wasn't downvoted at least once.
That's more likely to be reddit's vote fuzzing mechanism; any post with lots of upvotes will automatically get tempered with "fake" downvotes by the system.
Why? To counter some weird ass automated upvotes?
I have the notion that bad voters are canceled out by sticking in votes on the other count. That makes it harder for them to sniff out the fact that they don't really count.
Reddit uses a hellbanning system like HN. Spammers and the like don't realize they are banned until they try to read their own posts from another account. The auto-downvote system along with score caching makes it a lot harder to tell if your upvote/downvote went through or not. It's just one of the many, many anti-bot systems built into Reddit.