I was on a train from Parma to Modena recently, a local train. I forgot to get my ticket validated using the little yellow box before I got on the train. When the conductor saw that my ticket wasn't validated he said I could either pay him a 50 Euro fine, or he could call the Carabinieri, and I could pay them a 200 Euro fine. He didn't speak a word of English
I wound up not paying anything. I'm fluent in Italian
This happened to me between Ravenna and Bologna!
I don't speak Italian much at all but the Italian passengers in the carriage all turned on the conductor and told him he was being ridiculous as it was clearly an honest mistake by a foreigner. He wouldn't budge and I got fined €80.
One of the passengers then asked me if I'd bought my ticket from a window or a machine. He explained that the machine validates it automatically but the human in the window does not.
That is why I'd never been aware of the validation requirement before - I'd always bought from a machine except for that time.