I'm guessing the confusion comes from the perspective of the statements. I'm talking about 'one' a person in universe, you're talking about 'one' a player. One might expect a tyrannical magic theocracy to be nearly monolithic in it's culture and worldview, in a fantasy setting it can actually be monolithic. The other 'one', might expect that because this is a story being written for players to interact with, that every rule and expectation has an exception, the one that lets them be the exception. So it wasn't being a paladin that was unexpected, it was the cavalier way you had some random Gith being devoted to an alien god. "My grandfather was a gith, one of the
good ones".
Using the Gith as examples for this is strange to begin with. All the rules in FR become a little less distinct extra-planar, different types of allegory, cultures made totally out of time, and without historical antecedent. It's the difference between Medieval Fantasy and Space Fantasy.
These perspectives apply elsewhere. "Paladin" is a player term, it might also exist in-universe, but classes and the concept of levels don't. Everything to do with the mechanics of the game is an abstraction of what is going on in-universe, made so that a person with a twenty sided die can interact with it. In universe, people don't choose a class, their lives are mapped to the class closest to that abstraction. As with 'Common', it's not any language of Earth, but is abstracted onto our languages so that we can interact with the world.
Sozz="I think if you want to be the exception to the rule, it has to come from somewhere more than your backstory."
There are the exceptional circumstances you give yourself, and there are ones that come from choices you actually have to make. If you want to play a Githyanki paladin of Lliira, making it as easy as toggling the deity you worship over to Lliira, is a monumental character arc that occurs off-screen. It cheapens the choice, and by extension the strictures that make such a choice...'dramatic'. That's all, I suppose it's a little hyperbolic to say it 'has' to come from somewhere else, but maybe I've made myself more clear.
