I have been watching this thread develop with considerable interest.
I have no criticism of the FO who was doing the best he could with the resources he had available at the time and the experience, training and system which he had been exposed to preceding the incident.
But what I do criticise is the ethos and system which has produced this result. Flying is not an academic exercise but definitions of matters such as "V1" are. Many accidents and incidents in previous aviation history have proved that high speed stops are quite risky - lots of "M" and masses of "Vsquared" gives boatloads of energy to dissipate in one form or another - whereas continued take off at speeds close to V1 are usually much safer (hey why not use that energy to go flying?!). Does that mean I think you should never stop after V1 - NO! (but I'd have to have a damn good reason to do so!).
I would like to focus on another issue though. Over recent years we have seen a progressive attempted degradation in the authority of the aircraft Commander almost to the extent that decisions on the flight deck are made by consensus. Does this mean that I think the role of the FO is inferior? Of course not - a good commander will, when time permits, listen to the comments of the FO and if necessary act upon them to ensure safe operation. But we now have words such as "Advocacy" being banded about which lead some FOs to think this gives them licence to almost run the operation. This on top of all sorts of "touch feely" buzz words/phrases and acronyms to cover almost everything except how you walk out to the aeroplane is leading many newbies to think that flying is a "book" exercise and that the old codger in the left hand seat has to be pitied because actually "I know best because I've had all this amazing training" - in short, I see lots of overconfidence based on a system which attempts to codify and simplify what, in many cases, can only be learned from years of experience. Does this mean I think we shouldn't have procedures? No BUT it's the thinking that this breeds that everything is "cut and dried" - in short, I see much overconfidence.
In this case where the SOPs (in common with most other operators) specify that the Commander (left hand seat pilot) is the sole person who will action a rejected take off, he was probably in a better position to make the correct decision anyway as he wasn't actually flying the take off so he had more spare capacity to watch what was happening. He might have seen an airspeed trend arrow near V1 misbehaving but (rightly) decided not to call same since this would be an unnecessary distraction close to V1.
In closing, I have to say I find this incident very disturbing. I repeat that I have no criticism of the FO who "believed" he was doing the right thing but the system which has allowed this to happen.
In other circumstances this could have been a serious accident with the loss of many lives. The final question I would ask is, in this case who would have been liable? The a/c commander would have, in my opinion, a good case for saying that his authority and responsibility for the flight had been taken away the instant the FO elected to reject the take off.