Are usernames required to be unique?

Question

I recently changed my username to Undo. I was amazed when I pressed Submit and saw that it actually went through - surely someone somewhere was using this same username.

Out of curiosity, I then search the SO user list for Undo - and found another user with Undo as thier name. They have 50 rep. I have around 1,500.

Is there some kind of pecking order, I.e. a high-rep user can 'steal' a low-rep user's name? Or is this a bug?

Or can two users have the same username without causing the SO servers to go down in a burning ring of fire?

Answer 1

Accounts aren't tied to display names, they aren't required to be unique. However, if you participate in comments or chat with someone that has the same display name, you'll get a bit of noise in your global inbox if someone mentions one of you.

What you can't do is impersonate someone else, or otherwise harass people:

Under no circumstances will Subscriber use the Network or the Service to (a) send unsolicited e-mails, bulk mail, spam or other materials to users of the Network or any other individual, (b) harass, threaten, stalk or abuse any person or party, including other users of the Network, (c) create a false identity or to impersonate another person, or (d) knowingly post any false, inaccurate or incomplete material.

There's a difference between sharing the same name as another user, and pretending to be another user.

Barring that, there's no issue if several or more people share the same display name.

Answer 2

They're not usernames; they're display names. There's a big difference. A username is generally a unique string that identifies a user in the system. Stack Exchange doesn't use those; they use OpenID providers and a simple ID number. Your display name is merely an alternate string that more accurately represents who you are, and are rarely ever unique. They usually allow users to utilize a wider variety of characters, as well.

Answer 3

Usernames are not required to be unique.