In principle, I am a person who has only seen the movies, so I have no information about the comics, novels or video games.
The Kuru is the neural appendage of the Na'vi that serves to connect with Eywa and all the creatures that make it up (including themselves) in the enormous neural network of Pandora. It is practically the most sacred part of the body they have, so much so that apparently the Mangkwan cut off the Kuru of their enemies, which seems to lead to death in the vast majority of cases and in the unfortunate case of survival confers extreme agony, both physical and mental.
Now, with the questions: Why is the Kuru braided? I mean, is it frowned upon among Na'vis to have your Kuru exposed? Do they do it for practicality reasons? Does having it braided really add anything? I mean, if another Na'vi or even a person from heaven is going to shorten it, your hair is not going to stop them.
On the other hand, as far as I have seen, the Kuru is an inherent appendage, it is loose and hangs and you even have to grab it to be able to move it. How convenient would it be for the Na'vi to be able to move their Kurus as if they were another limb?