............ to get back to the topic - and it may be useful info to others. I have had a couple of certs near to expiry and given them to friends who are not Ambassadors or RAs who happened to be going to an IC for a single stay - hence membership wasn't attractive, but with the warning that they may not be honoured. Somewhat to my suprise both were accepted without question.
This does not mean that it will always work this way, I'm sure that some will experience differently
Very interesting!
Although, of course, there is also Plan B - which is that the Ambassador books the room, puts in the friend as 'Additional Guest' and then friend checks in first (and indeed last!), handing over the cert. Extra benefit of this is that the Ambassador will get the points as well!