@Scott177 , I would be a bit cautious as well. As far as I know the star ratings by hosts on guests is a fairly new feature, where a host is asked to give star rating to guests in 3 categories: communication, cleanliness, observance of house rules. In contrast to the public reviews, where usually you only find "nice" things posted, this gives a host more of an opportunity to be honest in their ratings, as it is not public. I would want to be a bit careful about the 2.5 stars you saw, what exactly it means, like did you see that as "overall", or did it not show you clearly the 3 categories I mentioned? (so maybe Airbnb changed it again.....?)
It is my understanding that this new star rating is not always displayed with or next to the potential guest's name, that it is only shown to prospective hosts when a guest makes a reservation request. After acceptance or decline it is not visible anymore. Just like prospective hosts are now shown a guest's cancellation history during the booking process, but not anymore after or before.
That just happened to me recently, that I saw a low mark about a potential guest regarding following the house rules, I couldn't exactly see or tell you a number, all I saw was that the last star had a subtraction on it, so I guess it was a 4.5 - which made it easier for me to decline her, as I had doubts about her promise not to get a third person into my place.But after I had declined her, I could not see the star ratings on her anymore . I never had a chance to explore further, or if it was on mobile only, or desktop.
If this new feature is here to stay, that would be a welcome help to hosts! Of course we all have to keep in mind that since this is fairly new, only guests who had very recent stays will have this.