Hi,
I think it would be cool to implement a feature which would allow users to group all their accounts, it would be very useful for sites like english wikipedia so that people could avoid being accused for "sock puppetry" (using more than one account) by marking the accounts as grouped, it is possible to create account in mediawiki so that you can see in log that it was created by someone else, but this log is available only for wiki where it was registered on and it's also not possible to mark account later in case you forgot to create it in proper way
Statistics of users would be also more accurate because you would be able to list groups only instead of all users and you would see exact number of users and not number of all accounts, including alternative accounts
This group interface could allow people to group their account anytime, the grouped accounts would be still completely separate, with different configuration, etc. But it would allow to check how many and which accounts someone have in a simpler way than it's now. (browsing multiple logs isn't really easy)
My idea is that each account would implicitly have a group which would be identical to its name, User:TestyBob would be a member of group TestyBob but it would be possible to change this group to any existing group, it would be of course needed to confirm this from target account, then you would just display members of group Test and you would see list of all accounts linked to the "main account", so you would know who is owner, how many account they have and such. I think it would be best to do this on a SUL level, so that it would work project independent.
Example:
User:Bob - member of Group:Bob User:CoolBotofBob - member of Group:Bob User:Bob (testing) - member of Group:Bob
in this case user has 3 accounts, grouped in a group Bob, it's clear that Bob is a main account of user
User:Peter - member of Group:Peter
in this case, user has only 1 user account which is a member of its own group
we have 4 accounts in mediawiki and 2 users in this scenario
When user bob create a new account User:B0b he could just change Group:B0b to Group:Bob and then confirm it from his main account User:Bob, there would be a special page which would allow to list members of groups, so it would be really easy to look up if user has alternative accounts etc.
Thank you for responses, it's just a proposal and it can be heavily changed upon your feedback.