Currently this special incentive of Google for promoting the most active GoogleSideWiki contributors is down.
See [GoogleSidewikiLeaderboard].
PS.: The author tested using the discussion part of Meatball to get timestamps. But this facility appears to be available only for a subset of the wikizens here. He had tested it several times, but his discussion contribution was rejected by the system each time. He got the system message: "Your submission tripped our defenses." Hoping that not other peers are affected by this :-)