I've flown a couple of times with Turkish Airlines and, the last time I had a long layover at Istanbul airport I applied to a free tour with Touristanbul. When I was waiting for the tour start at the Hotel Desk, I saw a lot of groups of people that were taken to hotels and along the tour somebody told me that they had a long layover and Turkish paid for a hotel for them. I had no time to ask at the Hotel Desk. I'd like to know how to get this free hotel, if it really exists.
Yes you have the right to have free accommodation in some conditions. According to the Turkish airlines website: