An interesting idea, I do not know if it has been taken up. In some orders, and this is a Flag of convience- in the convent, Nuns who are nursing sisters would wear a Red Cross ( which is also of course a Medical Charity- secular) on a white habit and this would stand out in the Hospital. this is more of a specialist insignia than, as you suggest a badge of rank akin to chevrons or campaign ribbons. As far as I know there are no active duty NUNS in the US Armed forces- there may be Nursing Nuns in the Spanish Military- and these would wear rank insignia on some part of their habits-This was done with the Spanish medical contingent in the ( Blue Division) who supported German and Spanish soldiers in nazi-occupied Russia, a strange saga indeed. as stated the US Armed Forces do not employ active nuns. Priests serve as Chaplains, of course, and are , along with MEDICAL men the only officers of the Army who do not carry, or have any practice with- firearms. Pistol packing padres are not found in US Olive Drab Army Greens!
The heads of convents are variously called abbesses, prioresses, and mothers superior, and a nun is generally addressed as "Sister."
Buddhist nuns (bhikkhunis) wear robes (civara). The robes have different names in different countries and different schools of Buddhism.
Different nuns do different things. Some live in a convent, others do community work for the poor, and others run orphanages. They probably all pray daily for some amount of time. It is cool to help orphans, widows, and the poor. There are Carmelite nuns, Franscican nuns, and Catholic nuns.
Different orders wear different colors, Benedictine nuns wear black, Cistercian nuns were white, and there are others. Regardless of the color, the entire "outfit", if you will, is called a habit, you can see more of an explanation at the link below:
Other nuns
Yes, nuns are women who have chosen to dedicate their lives to serving God through prayer, contemplation, and acts of charity. Faith in God is a central tenet of their religious beliefs and their commitment to living a life of spirituality.
Monks and nuns do the monks' and nuns' jobs now.
Yes, nuns can vote.
nuns
She is just a regular nun. Some nuns wear different clothing then other nuns just to identify the kind of convent she's from. Sister Mary Robert is a novitiate that is why her habit is different.
The nuns sleep in the nunnery in the convent.
Of course, nuns are people too