Originally Posted by
Boddingtons
I suspect you cannot block the seats via OLCI as you may wish for someone else to chose to sit with you that may not necessarily be on your booking. I would imagine only the check-in operator could perform this action.
Whenever I've OLCI'd, it has always shown the seat next to me as occupied. The first time I did this, I indignantly moved my seat! The map then refreshed and my original seat plus the one next to it were now empty and my newly selected seat plus the one next to it were both occupied. Although I'm heading towards being a bona fide 'Passenger Of Size' one day I'm sure, I'm not quite there yet

But then it dawned on me this is the seat blocking in action. It's never failed me yet (though admittedly, not a huge sample size) ^ This is how it's done at OLCI time.