Why did Soraka's recommended items change from Ancient Coin to Spellthief?

Same with Janna.

Probably because they think being aggressive will give you more gold since they removed the passive 1 gold for a minion dying.

Because Q has no meaningful MP cost, mortar 24/7.

you have no real mana costs if you take manaflow band, and soraka has naturally spammable abilities anyway. assuming you can consistently land it, its worth more then what coin would give.

ive always preferred spellthief with soraka [sg-zephyr]