Currently mails have no security on any mail headers like To, CC, Subject, References, ..., as those are not encrypted within the rest of the mail. So 3rdpary can modify those headers and can generate metadata on people. That's why people came up with the idea of putting another set of mail headers inside the encrypted and/or signed part of the mail. But now we also need to present this additional security to the users of kmail. And I think it may also be nice to give the user the possibility to switch between the different sets of mail headers.
Upstream has already released some screenshots of other programs:
both programs fail in my view to visualize the user what is going on and what headers are secured.
Hope @VDG has some good ideas how to make this right :D