I love the fact that characters are stored indefinitely so that former players can return, years later, log in and there ya go.
However, after all these years the "first name" of a character is what locks the character into the game. Absent the "unique" use of a surname we have new players/characters struggling to move past 'name already taken". So we see Bob, xBob, XBobx, etc...
By implementing a first and last name requirement we could see more custom names rather than "Ydddhdddd" just because it worked.
Much like in elementary school you were one of many "Roberts, James', Johns, Janes, Amys and the dreaded Heather's, that all had (usually) a surname that separated them from the other 16 they were in school with.
I know palindromes are creepy, but let us stick with "Bob" in our unique surname quest. Using a surname would allow players to create/recreate characters (if you are old like me) from the hay day of their PnP days... but yes, there will be a mess of Dritz's but they will have their own last name. So let's look at Bob again:
Bob Smith
Bob Jones
Bob Up
Bob Down
Bob Son of Bob
Bob The Slaver
Bob the Slayer
Bob the N00B
Does this create an issue in party? When you have 5 Bob's in a party? 5 clerics named Bob could be tricky to sort out which Bob you are after, but I am more interested in monitoring health bars rather than who it is. Finding Bob on the map might be tricky unless the map is updated to also show the surname so when I mouse over the blue dot I can see that it is, in fact, Bob Down that is incapacitated...