@Kelly149 I don't really put much thought into the star ratings for guests for one reason: they are only visible to hosts who use Instant Book. Maybe someday that will change, but the fact is that no host who really cares about screening guests would use Instant Book. So the difference between 3 and 4 stars shouldn't really be a factor for them. (If a mixed review would cause a host to cancel a confirmed guest, my advice would be to disable Instant Book altogether).
For the hosts that are selective with their guests, the written review is the one that matters. In that regard, I consider a violation of a house rule such as one against unregistered guests to be a very important detail, worth mentioning in the public review. I also think it's relevant to describe how the guest reacted to being told they had transgressed a boundary - did they correct the problem and apologize, or did they continue to be a nuisance?
I would not for a moment consider mentioning a private conversation that I was able to hear through the walls. That would send a signal to future guests that their private room is not really private, and that they will be judged for what they do behind closed doors no matter how they behave in front of their host.
If the sound of your guests arguing was disturbing to you, you could perhaps allude to it in the private comments, but personally I'd let it go. Despite being unhappy with what they booked, these guests chose to behave cordially to you as the host, and what happens between them privately is their own business. If everything else was generally OK, I'd say that merits a thumbs-up, and perhaps a caveat. My review might read like: "I'm not sure my room was the best fit for Homer and Marge, but they were considerate guests and left the place in good shape."
As for the other questions, I'd expect that at some point guests will be able to see the star ratings left for them, only because the law is gravitating toward people being entitled to know what data web companies are collecting about them. I default to 5 stars unless there's a serious problem (such as breaking the rules and bringing unapproved visitors over), and I generally hope my guests do the same. As far as I'm concerned, if people are paying for my hospitality it's part of the deal that I will accept their imperfections - whether they be marital drama, odd smells, bathroom hogging, weird hours, or other things that normal paying guests are perfectly entitled to. And in return, I hope that guests will recognize that I've provided the experience described in the listing rather than compared my humble home to the Ritz.
