Ah, yes! Modified dialogue tree, just for him. Perhaps the additional dialogue options are coloured differently to stand out; perhaps if you can raise your stats enough, then multiple improved dialogue options become visible as well. Brilliant, Lambonius!
Hmm... I'm seeing the sneaky bard now, in my mind's eye. In the case of Rayford slaying you on the spot (or sending you to the town square for beheading) you'd instead end up in the brig, by using your silvered tongue to save your life. Then, you'd need to talk Jan into letting you out for some reason (and complete a Jan quest to avoid later recapture). Perhaps none of your tricks work on Prospero; he's wearing a talisman of some sort that cuts through. Also, perhaps Rayford is particularly keen, so you mustn't conduct discourse with him directly, but through intermediary characters.