That is intentional - the idea being that characters with a reputation for being Good get an "always on" bonus to diplomacy, whereas other alignments only get the bonus with creatures of exactly the same alignment.
It's a Pathfinder game at heart, so there is no Gather Information skill - you use Diplomacy to gather information and rumours.
I was thinking Chaos = bluff, too (it's maybe easier for Choatics to lie without showing signs) - but I also thought maybe Law might boost bluff, because your reputation implies that you won't lie.