I co-host, and recently a guest did not show (and has not made contact at all). We are getting email reminders about leaving a review for the guest, but obviously cannot, because we never met!
My question is, are we obliged to always leave a review for guests? Does it reflect negatively on us (as hosts), if we do not leave a review?
You are not obligated to write a review and there is no penalty for not doing so. In fact, it's actually AGAINST Airbnb policy to review someone who never stayed. So you can just ignore the reminders.