Is Rand's choice of names in Anthem an example of symbolism, metaphor, or diction?
Literature can be interpreted in a variety of ways, but I assume you want one answer, so I will give you mine.
These names are symbols; they are symbolic of values that the society is trying, or pretending, to uphold. In doing this, they are stripping people of their individuality, making them objects of conformity with nothing to represent them but these abstract concepts. The names themselves represent the behaviors that the elders want the people to remember and to demonstrate. By having these "names" rather than personal ones, the people are constantly reminded of the way they are supposed to behave, in this case, for the greater good of society.
I rejected metaphor. Even though a metaphor is used to make an abstraction into something concrete to aid in understanding, we are not trying to compare the people to the names but to have the entire body of names represent the entire body of people. Likewise I rejected diction on the grounds that while words are examples of diction, choosing this as an answer seems too general. Many other abstract words could be used in their place.
I hope this helps.