As most of us know, Kev is retiring from being a moderator.
Kev has done an outstanding job in moderating Stack Overflow, and while he won't be a moderator anymore, it doesn't feel right that this isn't reflected in some way.
Expanding on that, Kev is by far not the only one who has contributed immensely as a moderator to the Stack Exchange websites, but is no longer a moderator.
That said, Gordon had the great idea that former moderators should have something to reflect that, a hollow diamond next to their name, like so:
So the formal feature request is, for former moderators that left moderating in good standing with Stack Exchange (it wasn't revoked for mod abuse or something of that nature), allow them to opt-in to having a mark (perhaps the diamond outline, perhaps something else) that will be attached to their username as a token of appreciation for the work that they've done in making Stack Exchange a better place.
This is simply embellishment on the username. It will confer no abilities in any way; the only privileges that they will have are the ones that they have due to reputation.