Actually, the likely scenario is that Microsoft employees make up a sizable portion of the HN user base (relative to smaller companies) and when an MS employee

Actually, the likely scenario is that Microsoft employees make up a sizable portion of the HN user base (relative to smaller companies) and when an MS employee sees something antagonistic towards MS, they downvote. Apple, Google, Microsoft, and Facebook to varying degrees all have the same phenomenon on HN. It's not the PR team, it's the eng team in their spare time.