And because corpse camping a.k.a killing someone multiple time on a short time is pvp, a dick move, but still pvp. But as soon as you do it for a prolonged time, a.k.a several hours/days.etc... it can be griefing, and Blizzard can look into it and may act and punish.
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What he provided was not a proof by any means. He provided a statement that Blizzard will not punished corpse camping. And rightly so as corpse camping is camping someone for 1, maybe 2 hours long at best. If that lasts more than that or even days, they may look into it and deem it griefing and act accordingly.