I've noticed some occurrences like this as well. For instance, the week before Bill Gates' recent AMA on Reddit, there were a a large number of frontpage posts

I've noticed some occurrences like this as well. For instance, the week before Bill Gates' recent AMA on Reddit, there were a a large number of frontpage posts about him from accounts with little to no karma. It's probably not the primary factor in opinion on him being drastically reversed, and I doubt he has any personal involvement, but it's possibly one of the tools utilized by his PR team.