Hi,
"you" means the address configured in the account, on the first account setup page (also used in the From line).
"View message source" -- no, and no plans... most of the time the app won't download original message sources (when using IMAP, I only fetch those parts that are needed).
"View headers" -- has been there for a long time... see the Menu when viewing a message or after selecting a single message in a message list.