Are answers from unregistered users with the same name from different people?

Question

I've asked a few related questions and got some reasonably high quality answers though there are still some bits to work out I don't grok.

I have the standard problem of being too technical to get many answers and too vague because I seem to misunderstand some fundamental concepts. That's irrelevant to this meta question and hopefully you guys will be more forgiving (re meta-effect) around the Christmas season.

I notice that all my answers come from unregistered users with the same name (Glärbo):

• https://stackoverflow.com/users/14779048/gl%c3%a4rbo
• https://stackoverflow.com/users/14849181/gl%c3%a4rbo
• https://stackoverflow.com/users/14862883/gl%c3%a4rbo

Is this because:

• stack overflow has allocated the same name? (maybe they use this name to mean 'an unregistered user')
• the user has used the same name
• the posts come from the same browser, e-mail address or IP? (and presumably would be auto-merged if they decide to register at some point)

The answers are higher quality than you might expect from new or unregistered user so I'm thinking this is someone who just chooses to remain anonymous and doesn't care about reputation etc. which is absolutely fine. I don't care too much about rep or anonymity except where it prevents me from offering decent sized bounties (which hasn't worked well for me anyway). However the different glarbo's also have different reputations from each other - all below the base level of 100. For a couple of the answers there is suspiciously copy paste out of a textbook feel for others there is much more thought. How can I be sure if I'm talking to the same person or not each time? I think you can't if they don't register. I have asked the user in a comment.

I am curious as to how unregistered users work. I see from this question (How does SO identify different unregistered users?) that cookies are used.

If I open a new private window for stackoverflow I see "post as a guest" has two fields an optional name and a email labelled "Required, but never shown".

So stackoverflow knows:

• if the email is the same
• if it selected the username itself

Some questions:

• Would it be reasonable for it to display this information?

(low value feature request. Obviously the email itself must remain private)

• What happens if you leave the username blank but use the same email?
• What happens if you leave the username blank and use a different email?

Answer 1

Most likely it's the same person, who just choose to post as guest:

The person always put same name and email (hence also same Identicon, which is generated using the email hash) and as long as they keep the login cookie, they're posting as the same unregistered account. However, once the cookie is lost (e.g. manually clearing it, or switching browser) a new account is created.

This is valid behavior; No harm is done. Answers are good, nothing is lost. If the person would like to merge them all, they can contact SE and ask for it.