It sounds like we may have similar setups. I host a suite that’s in the upstairs of my home.
I’ve overheard a couple people trash talking, arguing, or “I didn’t know it would be like (thing clearly stated in the listing)”. With some guests I’ve talked with them and ironed out issues. With others I read them as being insufferably miserable people and avoided interacting with them during their stay. Either way I try to review as if I’d never overheard them.
I confirm their guest count before arrival and have a “no unregistered guests” house rule, so sneaking people in is probably the quickest way for a guest to piss me off and lose stars. I’ve only given 3 thumbs down in a couple hundred stays and two of them were for sneaking in guests. I think I gave them 2 stars in both house rules and communication. I just don’t think that level of deceit is compatible with staying in people’s homes.
There are plenty of little things I’ll overlook – I ask myself if it was accidental or if I could have made the same mistake. Probably the most common is some noise after quiet hours. I don’t sweat a little wear and tear, so they have to be pretty careless or disrespectful to lose points on cleanliness. If they were bad at responding in a timely manner or really blew their ETA they could lose a star in communication, but sometimes I just tell them in private feedback.
I’m cognizant that many of my guests come from word of mouth and lower rated guests probably won’t recommend me to their friends. I’m also not going to pull a punch if they really deserve a low star. If someone is an entitled jerk I probably don’t want them referring their jerk friends either! I’ll always have expectations for how guests treat my home. Right now it feels like <5% of guests can’t deal with them – and good riddance. When Airbnb gets to the point that catering to the worst guest is more important than one of their better hosts (SH 13x…in a row! 5.0 average) I’ll pack up my toys and play elsewhere.
The ones I have the hardest time reviewing are good guests who were cursed with bad family members. One lady came for a wedding with her husband and his sister and bro-in-law. The in-laws were a mess!
When they returned from the wedding the in-laws were DRUNK and the sister was LOUD. I heard them trying to get her to bed in the room above mine. She threw herself down on the bed and collapsed through the bed slats onto the floor (she was a bigger girl and it was an inexpensive frame). Drunken braying laughter ensued as they tried to pull her out of the hole and my reserving guest whisper shouted "SHUT UP!! You're going to get us kicked out of here!!!" LOL.
The trainwreck also smoked in the garden, using my tea mug as an ash tray. I had a chat with the reserving couple as they were leaving and she was MORTIFIED. I did mention the issues in private feedback but rated the guest on her own merit. She tried her best.