The S/MIME standard describes how emails can be digitally signed using PKI certificates. Git recently gained the ability to understand S/MIME signatures, providing a method of Git signing that is friendlier to large organizations. GitHub is also now able to verify these signatures, similar to what has been done for OpenPGP signatures for some time. To make it easier for people to create S/MIME signature, we are also releasing a client tool called smimesign that is intended to require far less configuration than existing tooling.
You can now quote comments in issues and pull requests by choosing Quote reply from the comment’s options menu. This will paste quoted contents of the comment into the text field for the new comment. If part of a comment is selected, only that selection will be quoted. The keyboard shortcut for Quote reply is r.