Why not? It seems to me that it will be much better than concrete. Especially if you have a small child in your family. He will be much warmer precisely on such a surface. I myself ordered here such sheetmaterialswholesale.co.uk/mdf-board-15-x-1220-x-3050mm/ flooring material. Very pleased with the quality of my choice. So - don't doubt it
no not normal for flooring, but this is a pa site, not gernaral builders forum. but happy to help, go with a 18 or 22mm tng boards, far more rigid and stronger than mdf. Also the dust particles from mdf can be very bad for your health. what flooring do you currently have.