Oh really, maurin. It wasn’t meant as an offense; I was really asking. Never having heard the word in real life myself, I truly didn’t know.
I was a little confused because sedevacantist comes from the Latin sede vacante, which is pronounced SEH-deh vah-CAHN-teh. I would have thought sedevacantist would resemble that pronunciation, but you know, words borrowed from other languages usually undergo a huge change when they’re anglicized, so your pronunciation could very well be the correct one.