What is like the criteria to have IFC in your name. I know that display names are going away but still:)
There’s really no criteria at all - feel free to add “IFC” to your display name if you wish :)
People really just put IFC in their display name to indicate that the display name you are seeing is the same as your IFC username, makes it easier to find you and reach you on the IFC if need be
However this feature will not be needed after 20.2.