No, It is Immpossible. Localized strings can be used in many places in your code and user interface, only some of them can support rich text display. For example, UILabel has a text property that you can set from a localized string, but it cannot display rich text.
You will need to choose how to display the extended text in the user interface, and then decide how you are going to encode this text in a localized string. You may need to analyze the localized string and make your own text drawing, depending on where and how you want to display the text.