There's a difference between *imitation* and just having the same name.

 - ###Unintentional coincidence

    *Example: 2 people named John who create an account with the same display name. The profile picture will most likely be different.*

    This is the case when two users just happen to use the same name, and is completely OK. 


 - ###Intentional impersonation

    *Example: 10 blade19899's with the exact same name and profile picture.*

    This is not allowed and the imitators should be flagged with an appropriate message in *"other (needs ♦ moderator attention)"*.

    This is supported by the [SE Content Policy](http://stackexchange.com/legal/content-policy/):
    
    > **Identity Theft and Privacy.** Users that misleadingly appropriate the identity of another person are not permitted. [ ... ]