Heh, no you can say you like Cailean better than Kelsey without worrying about how Jason will react. The reason for the Anomen/Kelsey rule is that Jason created both of those and to have people say that the things he did for Anomen (a character he doesn't really like) makes them like Anomen better than Kelsey (his own creation)... well I suppose it's just a bit frustrating.
Hmm, I thought it was well, a joke.
NPC preferences are just so subjective there's no way any modder can expect to create a character everybody will love best of all. I love Minsc, Jan and Imoen, and I know many players can't stand them. But Haer'Dalis just flat-out annoys the crap outta me and a never play with him. Edwin amuses me, but I find the fact that someone is making a romance mod with him rather astonishing.
I'd also argue that if an NPC can be made so much more likeable with a few flirts, (okay, maybe more than a few) the problem was not that the character was designed to be inherently unlikeable, but that the execution was flawed.
(Holding up my "hey, Anomen's not so bad" banner whenever I get the chance.)
But I'm really looking forward to trying Cailean!
/feeble attempt to include some on-topic content.