I think one of the problems is the origin and the current.
Originally, in French, RSVP meant "please reply". But language is a living thing and it changes and evolves with usage. RSVP is not an English phrase/acronym - full stop. So anyone using it in an English language country, on an English language invitation, to English speakers and expecting a strict French interpretation of it, is actually in my opinion the one using it incorrectly.
In the US "RSVP" actually can be used socially as a verb to RSVP: "I RSVP'ed for both of us dear, we're going." "Jane never RSVP'ed, should I call her?" "Oh darn! I still need to RSVP!" And as often as not its used to mean a positive reply. Commercial/marketing events are often "RSVP only" which means tons of invites were issued, or maybe even a public ad was posted by way of an invitation but only people who reply can attend: Free Community Cooking Demonstration this Saturday, space is limited, RSVP only.