I'd noticed something like this on HN a few years ago. A negative comment about Apple might be voted up at first. Then, about an hour after posting, there would be many negative votes. The timing on this was consistent. After that, no more negative votes, and the rating would float up again.
I'll often see a similar pattern: I'll post something which disagrees with the common wisdom here on HN, it'll get a flurry of downvotes, then over time it'll get more upvotes. I figure that it's probably just the result of a few folks who are HN addicts, and that over time more reasonable heads prevail.
For Apple, it's so consistent that I suspect there's a program watching for negative Apple sentiment, then sending out alerts to people likely to respond in Apple's favor.