Besides, face-to-face communication can help you reflect on yourself a lot.
During a discussion, eye contact, posture and speech can show a person's confidence, persistence, ability and determination to win the debate. -- I seriously doubt that the posture of a person will show me their abilities. Look at politicians. They all have a respectable posture, they all make eye contact confidently and they all have perfect speeches. Their abilities? You tell me.
Also, discussion and debate are pretty different terms. A discussion doesn't automatically imply a challenge between two or more dialogue partners.
That is a reason why world conferences are not held online. -- This is great!!!