Is there a way to see if two accounts are the same?

Question

Is there a way to see if two accounts are the same? (I found some related questions on meta but not enough information)

Perhaps stackexchange uses some known techniques to calculate the probability that two accounts are the same (using cookies, source ip address, HTTP headers, ...)? (obviously these techniques can be fooled or can lead to wrong results, but in some cases they can be useful)

For example yesterday I answered an homework-style question Proof for ACYCLIC PARTITION being NP-complete (in the original formulation I thought that it was a completely different problem) and today I see a question by a new user that has a very-very similar formulation: https://cstheory.stackexchange.com/questions/21334/np-complete-proof-for-multiple-choice-matching

I think that the site should be tolerant in similar cases, but it could be useful to avoid spammers and disturbers (especially in other stackexchange sites that have a larger number of users).

Answer 1

I don't think there is a way for most users to find this out, but moderators do have tools at their disposal to look into such concerns. However, our tools are not fool-proof. For instance, consider the case of two lab-mates that both use cstheory. They would have similar questions (since they both work on similar problems), might phrase them in similar ways (since they might bounce the ideas off each other before posting), and would originate from the same IP. As such, it is a delicate issue and I believe that if there is not much problems being caused, it is better to give people the benefit of the doubt.

There is also a secondary issue which I think is even more difficult. A lot of people use cstheory under their own name, but the site also allows pseudonyms and such. Is it acceptable for a person to have a second account that is anonymous? I think this enters into a grey area. There is definitely cases where it is exploitative (such as vote abuse, etc) but also times when it might be useful (especially on sites like Academia.SE where people ask personal-ish questions).

I will look into the specific case you raised (although I won't comment more on it in either direction after I do, since I think such issues should be addressed privately as much as possible). Thank you for bringing it to our attention.