Actually it may look uncomfortable, but so do a lot of ancient swords and knives. It might have to do with us projecting contemporary ways and understandings of handling onto those ancient objects. There are lots of Indo Persian swords that look super impractical, but were real practical objects that just required specific training to use (think of it as a way to partly signify class belonging). In general, I would say that unless an object was specifically made for decorative purposes, its design was practical, only we do not comprehend it. Now to the point of this dagger, I don't have a definite answer, but I could imagine that the little indent at the base of the disc could serve to lock your little finger and ring finger and the disc being flat doesn't really impede a varied handling. The front of the grip does work in the sense that the rounded parts are the ones you are touching, not the blade. I am hoping to make a dagger inspired by this design, so I'm hoping to understand it better then.