Late Reply - sorry
Hmmmm - looks like I missed out answering this one: Can only plead workload as I'm presently in AKL training.
Certain exits, usually overwings but can be any exit where there is no crew member seated, are classified as "self-help" exits. Passengers seated at such an exit must receive a briefing from a crew member as to the safe and correct operation of that exit. The briefing must include instructions as to how to assess outside for hazard prior to opening, and how to re-direct if that exit is unusable.
If such seats are unoccupied, passengers must be moved into adjacent rows, in order that they can be briefed by the crew. However, if by moving passengers, the aircraft would go out of trim, clearly it cannot happen. The smart move would be to brief the nearest pax on the exit operation, and instruct them to proceed to that exit for completion of their duties if an incident takes place.
There are strict rules governing the allocation of seats in an exit row - the interpretation of those rules is to some small degree subjective and is massively complicated for all involved by the sale of those seats by airlines. All I can tell you is that I've never knowingly flown with unsuitable pax seated in such seats, and regularly move those that I am uncertain about.