Do you need the ability change the nickname?

there's even a comment can't be edited, and you're talking about nick)

Depends on where and why it is used, if only for the login, you do not need. But the ability to change the DisplayName most of this should be.

System, where username is the nickname, already dying(if not already extinct).
Separate these concepts and allow the shift Nik-Neumann if the site has entertaining. Otherwise, at your discretion(or the discretion of the customer).
Remember one thing — people love to change their "name"(nickname) and it adds the resource more freedom.

It is possible, but with a full history of changes to the public — the country must know their heroes :)

also just recently asked a similar question, or rather first, a slightly more advanced option — do I need a nickname at all if emeil for a login, first name+last Name for display on the website in the form of(Bob P.), came to the conclusion that you still need for more human identification in the user profile. so the url was /profile/id123456, a /profile/nickname is no copngrats creates on a server and users with clear and convenient. Well, now to answer your question — it all depends on the type of site and authorization methods on it. If the nickname used for login is better not to allow to change it, if just to display on the website(Display Name in forums IPB and vBulletin) — why not, the important thing to knowing the current nickname you could always tell the user, well, any functionality(such as bans) was not tied to the nickname. And last, it is important to design the database and the logic to avoid unnecessary queries.

In my opinion you need first, as already wrote to split the login and display name. At least from security reasons. The second is necessary to give the possibility to change the display name. This will give users more options. Especially if you are developing a forum or some social network. On habré it is not, because the Habr has quite strict rules and many here know each other by name. As for login — here it is best to think about the razor the okama and not to produce entities. Why separate the username and e-mail?
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Total: my version. email for authorization, the display name for communication on the site. To give the ability to change both.
If you can't or don't want to change your concept, remember that during registration, the user can simply mistype in username. If you do not give him the opportunity to change the name or even delete the account to register the right in that same mail he can just leave. It happened to me.

If they do, then the page the user has to bind only to the record id in the database
But, in my opinion, is superfluous. Will be a few times a day to change the nickname and shit where not falling. N if still necessary — maintain a log of changes and to introduce a limit on the number of shifts well, and may deduct points or karma for a change.