Matt asked this question.
Matt answered that question (which isn't an answer). Both are joined before a week so I assumed he's one person. They have both same gravatar.
and one more question - how did he do that? Two accounts, two email address ( = multiple openIds), right?
Well we know that the gravatar is generated based off the email address, and the 2 accounts are clearly separate (difference in rep, creation date, badges, tags, questions), so I would say your explanation is highly probable.
Two accounts with the same email address.
how did he do that? Two accounts, two email address ( = multiple openIds), right?
Both users are unregistered (it says "Unregistered User" at the top of their profiles), so they don't have OpenIDs. When he posted the question he filled out the Name/Email fields below the question body:
Then he lost his cookie, so when he went to post an answer he filled them out again, creating a separate account
You don't really need to post a whole meta question when you see things like this; just flag the question for mod attention and let them know the accounts should be merged