I've always thought same clan, same caste, as if you have different caste members in the same clan, wouldn't you have some affinity for them? And stemming from that affinity, you'd realise other castes aren't so different, really, so how could a civil conflict that comes out of inter-caste politics start so immediately and be so widespread after Delenn's actions in S3 in the Grey Council? Unless there's already heaping precedent that castes don't talk to one another. So it seems to me that clans as sets are fully contained within the caste. I always thought the 'warrior' who was the same clan as Lennier's buddy stole the uniform. (Though the warrior who had their uniform stolen might also suffer some kind of loss of honour.)

But! I can see an argument for the converse, as well - if one clan has only one caste in it, how do you split duties and roles? Lennier's Religious-Caste-Only clan seems like it'd defend itself well, but do they really call up a neighbouring Worker Caste clan when they need a building built?

On an unrelated note, I love that 'moment of perfect beauty' scene so much. I'd never thought of the monks being pak'ma'ra before, but I love that too.