No harms, it's a style of eating. I have seen many people eating curd and banana for different reasons.
Many of them said it makes them healthy as well as it's easy to eat.
The combination is not at all ideal but can be tolerated by our digestive system without any negative effect. If you have any digestive problems or your digestion is weak don't try.
Curd taken alone without mixing anything is best. Same goes with banana, should be taken alone. Curd shouldn't e taken with meat, fish, rice, beans, potatoes, or honey.