I was working with a customer and shared this information about the format in which user identity claims (aka user id) appears in any Claims based site. I shared below information with the customer and it appeared they didn't know about this until then. Sharing this information here for the greater community.
SharePoint 2013 and SharePoint 2010 display identity claims with the following encoding format:
Example: i:05.t|saml firstname.lastname@example.org