Comfort food seems simple enough to define. It's food that delivers comfort. Of course that sounds like a definition improvised by a distracted middle school student. How about, comfort food is food that feels like home. That's a little closer.
The more we send the concept of comfort food through our minds, the more elusive its meaning becomes. Striking an agreed upon definition may be an ongoing discussion, but viewing comfort food as ultimately personal and emotional provides a solid foundation for further dialogue.