C.E. Evans wrote:
Uhura's outfit seems to be an optional variant as there were also female personnel wearing full sleeves and trousers as well.
As we saw other Starfleet outfits that didn't feature rank insignia (the space-diving outfits and Kirk's cold weather gear), rank insignia may not be that terribly important to be on every Starfleet outfit. Even in TOS, McCoy and M'Benga's surgeon tunics didn't have rank insignia, neither did Nurse Chapel's uniform, or the formal uniforms (although some braiding along the front was used to distinguish senior and flag officers, IIRC).
I thought that was because a nurse is something like an ensign, not someone particular high in the pecking order. Ensign Chekov also doesn't have rank insignia. Having no braid on the long sleeve was in TOS and is in the movie a sign of a low rank.
Personally I find it stupid, that Uhura's uniform has no rank insignia. She isn't an ensign. They should have put something on the end of her short sleeve or on her shoulder or neck.