Handling users with multiple email addresses

[AndrewVSutherland]

A user can create multiple accounts for themselves using different email addresses. This is probably OK for the moment, but eventually we should think about whether we want to allow this and if so how to best handle it.

[rbommel]

What would be the problem?

[poonen]

I can't think of a problem that is caused by one person creating accounts with different email addresses.

But it would probably be more convenient for that person if we introduced a feature allowing a user to add more than one email address to a single account, with one of the email addresses being primary. Endorsing that user would endorse all the associated (verified) email addresses.