Board Thread:General Discussion/@comment-26158401-20160408123808/@comment-5811199-20160408124427

The poweruser group is, iirc, only used for Staff to find more active users and for displaying the Insights module on the right rail.

If it is still up to date, this comment thread explains that you have to have "made more than 140 edits in the last 60 days".

You may also find some info in Thread:810670.