It would be nice to be able to rechoose abilities, but you lose what you paid for it. That way you can try different things, or ditch a useless ability. But you have to repay. Or, even charge to get rid of one, then recharge for a new one. That would discourage ppl from selling.
We agree but the amount of coding it takes to get that in is currently not worth the effort. Unless you'd rather have Eirrmod working on 'depurchasing doctrines' instead of on new doctrine abilities

. Maybe in the future though.
As for the 'selling SP', must be a bug, oops!