That is, when you create D, you can link D to A, B, or C, but not A and B. This grants bonus AP to A,B, or C. Likewise, if you rebirth A, you can link A to another character (I have not rebirthed with a Hero talent since, so this is an assumption).
Flagship was one of the first of the traditional merchant account providers to offer free account setup, with no application or account setup fees being charged. The company was also among the first to offer true month-to-month contracts, with no early termination fees for closing your account.
Over the years, the term flagship has become a metaphor used in industries such as broadcasting, automobiles, airlines, and retailing to refer to their highest profile or most expensive products and locations.