I stayed at Riccardo's place twice and will definitely stay again when I am next in Bologna.
For starters, it is so centrally located. Everything is a walking distance away. Piazza Maggiore is literally across the street.
The space is very efficient, super clean, I guarantee you will feel at home here.
Finally, Riccardo is the most attentive host I have stayed with during all my Airbnb stays. He is there personally at check-in, has documents providing a great introduction to Bologna, provides ideas for dinner at all ranges, etc.
If you are looking for a place in Bologna, I would highly recommend booking this place.