Setting aside content-based restrictions, how do and should games implement names? That is, what text can you enter into that field?
Options here include whether the game allows spaces, numbers, punctuation, or other special characters such as letters not used in that language, smilies and hearts in the character map but not on standard keyboards, etc. The issues of which letters/characters to allow will vary by language, and spaces and punctuation affect the chat system.
A minor but annoying effect for non-monogamous MMO players is remembering whether this game includes last names as names (or just decorations, like a title) and whether this one demands something after the name when sending tells. If the game’s names are one word, no space, then you can “/tell BobBlunderhammer Hi” just fine, while spaces demand a comma or such: “/tell Bob Blunderhammer, Hi” so that the game knows where the name ends. Otherwise, you might want to send Bob a tell of “Blunderhammer Hi,” the traditional greeting of dwarves in the Blunderhammer clan. If you can include punctuation, you need some way for the system to know whether that comma is part of the name or the message. See also Little Bobby Tables.
Beyond the programming, all options involve disadvantages in-game. The use of similar-looking characters is a special annoyance, such as grouping with Mégan, Megán, Megån, and Меgaṉ or sending them tells. The last, in case your system is not showing it, uses Cyrillic characters that look just like M and e. Even restricting it to the 52 Anglo-American characters, let’s hope your capital I does not look like your lowercase l in the default font. Frankly, these people get what they deserve if no one can invite them to groups, although that social restriction is reduced in these days of random dungeon finder and clickable names.
See also name confusion, intentional or not, from names that are similar due to capitals and special characters. You would never notice that Меgan was impersonating Megan unless you recognized the Cyrillic letters.
Putting last names in separate fields makes them irrelevant to most interactions. You send /tell to Alack, and no one in your guild who has not “physically” run into your character knows that his last name is of Ofpie. Similar issues let Hugep Ennis evade the name filter or being reported for a long while.
I find decorative punctuation annoying, but apparently many people think that -=-Killer Assasssin-=- is a great name. Without punctuation, or spaces xXxKillerAssassssinxXx works like a charm. If I could hate them to death, I would.