Maybe this is already well-known, but I saw another behavior recently on some subrreddits where a lot of new posts are seemingly getting a single downvote to a score of zero. I suspected there was some troll doing it, so I went down the line and gave about 20 or 30 of them a single up vote back to one, refreshed the page, and most of them had immediately gone back to zero. I think the mods must have a button for squashing a post without actually deleting it, and on some subs they use it for a huge number of the posts.
There is also just a massive amount of bots on reddit. Unidan, a old famous redditor, was involved in a controversy where he would use bots to down vote all the posts made at the same time as his own posts so that his posts would be more visible. He's not the only one doing things like that
13of40 was talking about a single button that mass downvotes multiple comments. None of the default (nor popular) clients support this functionality, but you could script your own version using the reddit API.
> I think the mods must have a button for squashing a post without actually deleting it
No, Reddit does not provide such a feature. And setting up an outside bot farm to hide posts makes no sense for mods who can already just delete a post outright.
