Often1

While the Covid-19 situation may delay implementation, carriers are working through IATA to implement "better" transmission of baggage information so that these fees can be charged by onwards carriers. The problem here is, of course, that OP did not wish to check the additional bags, but had no option because AC could not physically accommodate the bags in the cabin.

But, the larger issue going forward will be that onwards carriers may well no longer honor all manner of bag waivers when not applicable to them, e.g. status, class of service, credit card, and other waivers. Many more passengers may find themselves being asked to pay fees by a connecting carrier.

This particular situation is unfortunate because I am fairly certain that it never occurred to AC personnel that gate-checking those bags would result in $600 fees by NH. Similarly, NH likely viewed this as a failure by AC to collect those fees when the bags were checked,

gengar

In the interests of accuracy, as per OP there was actually plenty of overhead space in the cabin; they were forced to gate check by an AC gate agent at YYC under the claim that the flight was full.

Inappropriate inanity aside, it was 8 checked bags and 3 carry-ons for a party of four, and the carry-ons could have been any size.

Often1

It isn't going to matter whether there was space. Carriers routinely require gate-checks when it appears that there may not be enough OH space because it is easier to gate check at the counter than to have people / cabin crew schlepping bags up front when it is time for the flight to close.

Bottom line is that other than those who board early in the process, gate-checking is a problem.

gengar

I never suggested this was the case.

Vangrovsky

I must be in the minority because I'm always happy when the gate agent wants to check my carry-on bag. I do not like dragging my carry on the plane or through the connecting airports. I do not mind waiting for my bag to come out at all.

I was actually in the same situation as the OP once. IAD-ORD-LAX-NRT. I checked three bags(first 2 free, paid for the 3rd). The UA gate agent forced almost everybody to gatecheck their carry-on bags because the flight was truly 100% full and it was a tiny A320.(when I boarded, there really was no space)

At LAX, the ANA agent pulled the same stunt and demanded that I pay for excess baggage on the 4th bag(the carry-on. I just told her that I had already paid it in cash to UA at IAD. She didn't question me any further. So I basically told a questionable half truth....

UAConcorde

Okay ANA really should stop doing this. Having all other carrier issue a receipt coupon for a gate checked bag is just not practical

Often1

That would not have helped OP. The point is that AC gate-checked his bag and, quite properly, did not charge for the excess baggage. Having a receipt would have done nothing for OP as it would have been for CAD 0 and thus NH would have collected the excess bag fees.

sethb

Having a written statement from the GA that the bags would be checked to the final destination free of charge should make it easy to collect the baggage fees from AC.