Interesting to read the harder data on the actual merits of each element. Coming from a digital marketing background, I actually do think there are other points that Airbnb definitely adds to the mix that you might not be thinking of. When we're building landing pages, we measure interest by what's called "time spent" on each page, and "bounce rate." There is no doubt in my mind that Airbnb uses these metrics as well.
Time Spent is pretty self-explanatory: it's the amount of seconds a user spends on a given page; Bounce rate is the number of users who navigate away from the site without viewing other pages in that session.
Those are metrics Airbnb uses on their site as a whole, because the longer a user is engaged with the site, the more likely they are to convert, which is Airbnb's goal. They don't care who's property converts users—they just want that user to convert. If your property engages viewers (reading descriptions, looking at your calendar, viewing photos) then Airbnb must (!) weight that property as being "stickier" and therefore wants to send more users to it.
So what's all this mean? Well, my hypothesis is that listings with better content will hold attention longer, and will naturally turn "browsers" into "considerers" and, ultimately, "converters." And, I'd bet Airbnb would push those listings to the top.
Just a theory, but one based on some of the more hidden aspects of internet marketing...