Do you know for sure that there is reciprocal boosting going on? I wouldn't know who nominates me, and I wouldn't know how to tell when a story has been boosted unless it's listed in the Medium picks.

If there is reciprocal boosting going on, that would be very unethical.

I do know one very mediocre writer is getting a remarkable number of boosts, so they obviously have a fan among the nominators. It's all very subjective though. What I think is mediocre, someone else obviously thinks is brilliant.