@AffableGeek I didn't ask him about Patripassianism. Perhaps I should have brought it up, so that I could give you a "response from the priest" on that, but I think this page for example:
newadvent.org/cathen/10448a.htm gives some account. If you go down a bit on that page to "Modalists", you'll see that the main point there is a confounding of the Persons.