For the frequent cases where a user ends up with two or more accounts (e.g. me on mojoportal.com!) an administrative utility to merge these, specifying the account to keep. This would reassign posts, merge roles, reassign authored features and pages, store purchases, etc, and finally bin the old account. I think duplicates often arise due to use of social sign in alongside manual registration.

This could be initiated by user request and carried out by an user with permissions to manage users.

Even better would be to facilitate and even automate this, and here's one possible way, which would be simple for the user while still preventing users hijacking other accounts: perhaps within "My Account", a tool to "Request Account Merge" which asks them to identify the account they are signed on as either "to keep" or "to delete", and enter a "pass code" for the deletion (a string which simply serves to cross-reference the accounts to be acted on). When they save this, we check for other accounts with that passcode, and check whether we have a target account specified, and if we do then the user is shown a confirmation warning and the merge takes place automatically (without admin action). If we do not, the user is shown feedback with guidance that they must mark at least two accounts with same passcode, with one account flagged as "to keep".

Thanks for giving it some consideration.

I wonder, could you by any chance merge my two accounts ;-?

I was only kidding really, as I imagine this hard graft (hence my o.p.). But if it is possible then I'd keep the account that has our purchases - it's associated with an @esdm.co.uk address (not the one I am signed in with now). Most of my posts are associated with the @live.co.uk account and I'd want to keep them.

On a related note, would it be possible to enhance an existing account with more ways to sign in? On StackExchange, for example, you can add different sign in methods to your account, e.g. Google, Facebook. I believe they use Janrain.

I know it is already possible to add an OpenID to an existing account, but I can't seem to enable the nice things described on this documentation page https://www.mojoportal.com/using-openid.aspx - the settings form is not as shown on that page, and www.idselector.com no longer exists.

And on a site with Janrain enabled, I still cannot find a way to add a social sign-in to an existing account. Where the email addresses match, it appears to nicely map the social sign-in to the existing account, but often it doesn't (e.g. Google, Yahoo, Microsoft will all want you to have their flavour of email).