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I have seen xecency, but have no idea about it or them.

They are a facilitator of the crab bucket.
Part of the duty of being a hivizen is to claw back rewards from 'overrewarded' posts.

By following their downvote trials on hive.vote you can counter what they take from the pool.
Here is a post I made about it: https://peakd.com/thehive/@antisocialist/the-daily-meme-372.

You can follow them with a small fixed vote to register dissatisfaction.
Just add an x to the names in that list.

If those 20 accounts stopped voting, everybody else's votes double.

I didn't know that xaccounts were created for this purpose.