What's the use of System.String.Copy in .NET?

Question

I\'m afraid that this is a very silly question, but I must be missing something.

Why might one want to use String.Copy(string)?

The documentation says the me

Answer 1

string a = "test";
string b = a;
//Object.ReferenceEquals(a,b) is true
a += "more";
//Object.ReferenceEquals(a,b) is now false !

auto-change detection ?