What we do not claim
No certificate belongs on this page, because none applies — an invitation site is not a bank, and pretending otherwise is how people get caught out. What is true: guest answers go to the host's list and nowhere a guest can see; the page is yours to edit or gate at any moment; the reply form asks what the event needs and nothing more.
Judge that against what you are actually protecting — a dinner's guest names, not a medical record — and the arrangement is more private than the habits it replaced. A card left on a noticeboard, a chat group where every member can screenshot, an email landing on a shared household inbox: none of those carry a password, and all of them travel further than intended.