About the simplest method would be to make your own custom sprite font out of Sprites.
One letter per frame and have the special characters have their bounding boxes be bigger than the other letters. You would then compare the frame, or instance variable when the frame is clicked.
I assume you already figured out the parsing.
Making a custom size bounding box would be another matter as you cant change the width without changing the texture, unless you use a mesh, or a hierarchy.