I think at times the bags are not tagged (no matter if you pay for the full fare or are upgraded) since the agents know the cities you are traveling thru will never honor the tags!!

MIA and JFK are known for IGNORING the orange tags. Supposedly if the flight is what the staff consider a 'true international' flight they do obey the 'rules'. KIN is technically not international .. so at MIA it would be catch as catch can.

I know JFK-BDA (and even last week MIA-BDA) the premium tags are ignored.

That said, ORD-LHR (or reverse) the tags SOMETIMES will mean something . sometimes NOT.

If the agent forgets to put the tag on ASK! You know the drill .. and say .. 'well sometimes it does help'. I was on BA from AMS-LHR in steerage connecting to LHR-ORD-MSP with upgrades. I had no right to ask BA to Priority tag my bag .. but I said 'Im in Business across the Pond, can you premium tag them' and there was NO question. YES that trip helped.

I have also been told by baggage staff .. that One World Priority tags ARE ALWAYS given priority .. and that only sometimes the orange American Premium tags seem to be. WOW .. they ignore their own airline's bags to deference to OneWorld. Go figure!

Help . maybe. Hurt .. probably not. If not tagged .. technically it seems connecting bags are loaded as they arrive .. to be topped off by originating bags. You can sort of tell the AAA-BBB-CCC will have LOT of BBB-CCC bags off first .. then the connecting bags.