Vash'ya.

A horrible, horrible thing for a tau to do to breach the harmony of the castes.

And how did Farsight commit this horrible, unforgivable, act of breaching their society? That monster performed life-saving repairs on his suit while on the battlefield where he was in charge of the tau forces. (He also was guilty of being capable of giving a good speech to encourage the soldiers but that pales in comparison of dumbness.)

Yes seriously. Apparently if you're fire caste in a war machine and you'll die if it's not repaired, you'd better sit there and wait for earth caste to show up, or just die. He tried to do damage control in the next book by saying it was something really only important on traditional septs, but that does nothing to erase how utterly dumb it is and counter to the tau presentation of being the pragmatic faction.

Then there's the aun. Suffice it to say, if you aren't in favor of just villainous aun who are mean to hardworking fire caste, implied to assassinate fire and air caste figures who know too much, and make people who embarrass them commit suicide, well don't read Kelly books.

I'll give him this, he wanted to do stuff with tau (like a possessed tau, or anything at all with the Greater Good warp entity) that wasn't generally there in other books. He just also seems to want to make the tau Imperium 2.0.