I've only ever flown with a companion in CW and been in the fortunate position of knowing the person through the divide (being the one who does the OLCI I tend to get the better seats ).

It may be uber-polite to ask but if you want privacy you are entitled to it, even if the other person objects (which I assume never happens). On a long haul flight, the 5 seconds of awkwardness will be more than made up for by the hours of privacy.