Hi there,
I think I read before that to select seats you had to be an Asiana Club member. However, when I went to online seat selection, it had a guest option. I've clicked on "next" and "finish" and it seems to have saved my choices using the guest option. We'll be in Y on a 777-200ER. Would there be extra choice if I went to choose a seat as an Asiana Club member? I chose the two aisle seats of the 3 seat aisle column and it blocked the middle seat.
The guest option seems rather insecure

I have a friend who's also travelling on the same plane. I see that my selection appears to be reserved, but the middle seat I mentioned above isn't blocked. Obviously, it'd be rather undesirable though. My friend seems to have more choice. Would that be down to his ticket type? I bought Q class. Or could it be because he's a club member? I suppose I could just join and find out.
To answer my own question, it would appear that membership/guest seat selection makes no difference at least at the lowest silver level. I think my friend bought a higher class ticket.