A few persuade checks don't produce any different dialogue, even for characters with high persuade. I'm unsure if there's just no alternate dialogue to be had (in which case, perhaps remove the [Persuade] tag from the option, to stop people feeling like they're missing out on something), or if the DCs got a few extra zeroes added to them.
The following was tried on a PC with 97 total persuade, substantially beyond what most builds can expect to achieve without hideous overspecialisation.
