Thanks for the compliment! I must be lucky, because borage flowers taste consistently, lightly sweet to me. As with most plants, each person's sense of taste is going to vary a lot. I have a hard time with bitter foods, for example, because I can REALLY taste the bitter.
The leaves aren't naturally sugary. What you do is chop up leaf, stalk, and flower, and soak them in water for a few hours. I think I went closer to 10 hours actually. A friend of mine who was also trying out the recipe only soaked hers for a couple of hours. Results were similar. Then you use that water to make a syrup, adding sugar in until you reach the desired thickness. The sugar is where the sweetness comes from. The borage adds flavor and a light color. It's nice on pancakes, ice cream, or fruit tarts as a glaze.