@Ange2
Those are both interesting points. I hadn't noticed a marked difference in the reviews. I do remember one young guest who left a positive, but strangely flowery review, but he was an aspiring writer! Then again, I've had guests, both young and old, leave very detailed reviews and also very short, succinct ones.
You are probably right about the solo traveller part. They tend to be more interractive with the host and, with a few exceptions, have paid more attention to the listing. But, I've hosted lots of couples like that too.
RE the culture thing, I mean to say that there are some things that might be considered normal in one culture but not very polite in another, and misunderstandings can arise if either party aren't aware of them. Sometimes it's maybe a case of culture + age.
For example, I've hosted several pairs of young girls from Korea, but only one older guest (a middle aged guy). He was very interested in learning about other cultures, so we had some quite interesting discussions around this. I learnt quite a bit too! I had no idea that dishwashers were such a rarity in Korea for example.
However, even though he wasn't doing it himself, he was totally baffled as to why I would object to these young guests blow drying their hair, slamming doors and making other loud noise at 3 am when other people are sleeping. In the UK, it would be considered rude to behave this way, but he couldn't understand why.
I am not saying that certain nationalities make good guests or bad guests, just that there are cultural differences, including how we communicate, e.g. in some countries it's not considered polite to be direct, or to say 'no'. The more the guests and the hosts are aware of these differences, the more smoothly the stay is likely to go!