Dealing with unregistered users answering their own questions with another account

Question

Occasionally we'll get Unregistered users come back to their own questions with a different account. Perhaps they flushed their cookies, or maybe it was at work and now they're at home. Either way, we have an original-poster attempting to add information to a question using an account that isn't the one they posted the question as.

How do we handle these?

Answer 1

In the past, it was dead easy:

1. Flag for moderator attention
2. The Moderator will check to see if the two really are likely belonging to the same person.
3. If it looks like it, the moderator will merge the users.

Only, that doesn't work anymore. A few weeks ago the Stack Exchange staff took away user-merge as a moderator power. Mistakes were made, and they require very fiddly database picking to undo. This gets really bad if a moderator doesn't exercise enough care and merges a 7000 rep old-timer into a 1-rep newly-registered user. Also, user-merges are SE-wide so the same accounts would be merged on StackOverflow, SuperUser, and anywhere else the two overlap.

User-merges are now a user-directed action. They have to:

1. Go to the Contact Us link at the bottom of every page
2. Select the Merge User Profiles option on that page

This will notify SE staff that a merge needs to be done, and they'll do it. To my knowledge, there is no way to notify SE staff on behalf of a user that such an action needs to be done.

So if you come across such things:

• Leave a comment pointing them to the user-merge link.
• If this is content that should be in the question, put it there yourself or mod-flag.
• If it's an answer to the question, also point out they can accept it themselves after their accounts are merged and 2 days have passed.

Answer 2

How do we handle these?

TL;DR: We do not.

Only SE Employees can handle this now.
They only handle requests from the user who created the two accounts.

You can leave a comment for the user, but if they're careless enough to create multiple accounts it's highly unlikely they'll go to all the effort required to merge account.

UPDATE:
Let the backpedaling being... Now Moderators can fill out the same form on behalf of users when the users, who weren't likely to come back in the first place, never request it themselves. So Moderators can jump through more hoops tha before, request an Official SE Employee Stamp of Approval™, and get'r done... again