That it has been morphological reanalyzed is demonstrated by the fact that it takes regular English verb endings, as in:
"I RSVPed yesterday, right after I got the email."
As I said, it is now a bona fide English verb, and most English speakers will treat it as such.
Didn't know that. Is this a very recent use?
In France, I think that RSVP was introduced and widely used at end of telegraphic messages (that contained lots of conventional acronyms), it survived at the time of telex, but now it is renewed with SMS messages on cellular phones, but is rarely used in emails.
May be this was introduced in English at the old time of telegraphs as a useful abbreviation, but with a different meaning when it is used as a verb for saying "reply as requested"?
