I'm not sure how to fix all the issues outlined in this article, but I think that a 14-day, double-blind review period started at checkout would alleviate some of the trust issue presented here. That is to say:

Once checkout has completed, both Guest and Host have 14 days (21? 30?) to write their reviews (neither party can see the others' review). At the end of that period, both reviews are visible on the site and cannot be edited.