He is unable to convey how he feels with the usual tells in facial expression or tone. The tele-vision shows faces and makes beeping sound for him.

[ At first, Nen had thought that maybe he was actually some sort of human-shaped computer interface...but that idea went out the window pretty quick when, you know, He took the helmet off to eat. ]

I think he is fine without it. But he likes it.

[ And they are 100% okay with that. ]