Update: it appears as though the Insert Formula box is changing my quotes to another font.
I enter a formula as: concat(substring(today(),6,2), "/",substring(today(),9,2), "/", substring(today(),1,4))
and it converts to: concat(substring(today(), 6, 2), “/”, substring(today(), 9, 2), “/”, substring(today(), 1, 4))
Notice the change in the quotes :-(