I don't see how that would fall to different people in reddit's case. I'm sure reddit has some moderators on staff but the vast, vast majority of their moderation happens on the proverbial front lines, which is basically all volunteers. I would hope there's a dedicated abuse team at Reddit that are actually paid people whom the volunteers can kick the truly sick shit to so it can be properly dealt with, but given the corporate culture Reddit has shown over the years, I also wouldn't be awfully surprised if it's JUST down to the volunteers either.
Reddit outsourced most of it's moderation to unpaid volunteers.