I don't know why but first Console.WriteLine returns reversed string whereas second returns prompt "System.Char[]" instead of reversed string.
string name;
string reversedName2;
Console.Write("Enter your name:");
name = Console.ReadLine();
char[] letters = name.ToCharArray();
Array.Reverse(letters);
String reversedName = new string(letters);
reversedName2 = letters.ToString();
Console.WriteLine(reversedName);
Console.WriteLine(reversedName2);