No tricks ... Insert Text script step can't accept calculations or formatting.
I suggest instead that you use Set Field which allows you to set a field with a calculation or Insert Calculated Result. Set Field is usually best because the field doesn't have to be on the layout for the script step to work. Insert ... requires the field on the layout.
I was able to insert bullets (•) by keying <option +8> so I was hoping to use similar trickery for bold, but oh well.