Seriously, their society sounds so overtly positive in the face of a preposterously hopeless and uncaring universe, there’s no way even the codex is telling the truth.
It’s like being stuck in a malfunctioning elevator with the Adoring Fan from Oblivion, or trapped in a burning home with Ned Flanders; the overt positivity just seems like it’s projection and there is a hidden darkness element somewhere waiting to come out.
The “Greater Good” religion simply sounds too good to be true. So they should all be destroyed, and their societies wiped from existence.
Edit: it looks like many people here don’t understand the obvious hypocritical irony and sarcasm written here…
Less social mobility than the people with hereditary nobility? It’s not great, but the IoM are pretty poor at it. I suspect you misunderstand the T’au caste system; admittedly it probably shouldn’t be called that as it doesn’t really function like a real world caste system.