@Loretta55 This is a very easy one to solve. All you need is a minimum stay of 2 nights or more. Nobody wants to pay for two nights just for a one-night stand.
Those who are particularly squeamish about evidence of sexual activity can also choose to rent solely to solo travelers, although of course there are plenty of ways a solo guest can also leave unwelcome evidence.
There's no reason that "hook-up" guests can't leave the room in an acceptable state. A waterproof mattress protector, a prominently placed, lined wastebasket with a lid, and good ventilation should be enough to make this a normal cleaning job.
I personally don't think there's anything wrong with an early checkout, if the booking is paid in full. And I consider consensual sex between adults to be a normal and legitimate use of a private bedroom, as long as all participants are registered guests. Your intuition is correct that it's not acceptable to mention it in a review. However, hook-up guests should be held to the same standards as any others: they should be honest about their party size, follow all the House Rules, treat the host and home considerately, and leave the property reasonably tidy. When they fail on any of those counts, it's OK to mention that in a review without exposing private details.