The API REF for GoText.Bordered says:
The line drawn around the text is drawn using a solid Pen whose color is TextColor. If you need more complex borders, wider margins around the text, or other visual effects, you will need to override Paint(Graphics, GoView) or compose different objects using a GoGroup. Note that the Bounds of this object are not changed by setting this property. However, this property does affect the result of ExpandPaintBounds(RectangleF, GoView), just as the Shadowed property also affects that method.I wouldn't actualy recommend overriding Paint.
GoTextNode has margins, depending on what you’re doing, you might be able to use them.
One idea the API REF doesn’t mention is using a Compound Pen, where the one side of the pen is the same as the text background, and the 1 pixel on the outside is the border color. that might work. As it says above, that does not expand “Bounds”, which might lead to other issues.