> That's why we keep your verified mailbox address for sending mail; but there's no good reason to consider them different for the purpose of identity.
Both of Microsoft's own identity services (AAD and Live ID, and by extension O365 and Outlook.com) recognize (and allow creation of) microcolonel@example.com, micro.colonel@example.com, and mic.rocolonel@example.com as distinct identities/email addresses.
What you're saying is that once the first of (microcolonel|micro.colonel|mic.rocolonel)@example.com registers at github, the other two will no longer be able to do so, but will instead receive a confusing 'you already have an account' error, (hopefully) without being able to receive password reset emails.