how can people think the cable dont have any safty issues, if the bolt as taxi al says is locked over is in place but the one side that stops the seatbelt moving isnt the rear seat will twist and bend in event of a accident, think back to the adverts when showed a accident of a unrestrained person in rear hitting front seats, wasnt it the force of a elephant or simlar, well all that will be pulling on a unfixed area that is designed to do the load bearing, do your own maths
How is that any different from using the outer belt with the seat in the same state?
The point I am trying to make is that with both ends of the seat LATCHED and the centre bolt in place, the seat will NOT move.

If the lock button is fully up then the seat is latched. It's really that simple
The centre belt has two seperate mechanisms:
1. The inertia reel, which stops the belt from pulling out under load. This is the safety part and is unaffected by disconnecting the cable in question
2. The tilt switch which locks the reel when the seat is out of position. This also locks the cable release when the seat is unlatched.
NO ONE is suggesting using the seat whilst it is UNLATCHED as that would be criminally insane, surely

id be happy to do anyones too if stops them removing parts, wonder how many would remove the bolts out the drivers seat and drive down rd,
WTF?
If the mechanism is sticking through age/lack of use/worn out, disconnecting the cable is neither here or there. Common sense dictates that when you put the seat back up you check that it has latched in the same way you check the bonnet is properly latched when you shut it...
Just my thoughts, you don't have to agree

p.s. A firm thump with the flat of your hand just below the button on the face of the seat will usually see the lock button rise up to the top of its' travel.