Brion Vibber wrote:
IMO we should strongly discourage use of multiple
accounts with the same
email to the point of forbidding it in software for new accounts.
MediaWiki currently has constraints requiring that user IDs and user names
be unique. Why make user e-mail addresses unique? As you note, it's a
fairly low bar for users to bypass such a constraint and there are
use-cases for allowing multiple accounts to share an e-mail address.
Figuring out how to migrate those old accounts is
something that needs to
be considered and worked out, but it shouldn't hold up work on making the
login/reset form accept email addresses for the common case.
I believe password reset via e-mail address is already implemented. :-)
 I personally have a bunch of test accounts that
probably have the same
email, and I'm sure some folks have bots and other things set up
similarly. Note that many email providers including Gmail allow email
aliases with "+" and something else after your mailbox name, such as
'johndoe+testing99 at wikimedia.org'; I've used this in the past to have
separate accounts on one email for Apple and other providers as well.
It's probably difficult to estimate, but I wonder what percentage of users
are currently using a mail provider that supports this type of behavior.
On the one hand, I thought Gmail/Google Apps was alone in supporting
account+something(a)example.com functionality, but on the other hand, nearly
everybody seems to be using Gmail/Google Apps these days.
I also wonder how many users would be affected by making e-mail addresses
unique on a large wiki. That is, how many instances are there of two or
more accounts using the same confirmed e-mail address on the German or
French or English Wikipedia? We should be able to query this information,
which I think would provide useful context and understanding.