Originally Posted by
Lux Flyer
Also, regarding first class vs. premium select weight/bag allowance. Unless your wife is on a split fare, her fare is a premium select that has the domestic segment in an available first class seat (there are accounts of a premium select seated in domestic Y when first class seats aren't available), but the underlying fare is still premium select. So, no she doesn't get 70# going over, she gets 50# because that is the allowance for the premium select fare she is flying on.
I don't think this is at all clear. In my experience, Delta baggage policies are related to the
cabin of travel, not the
fare. I say this because passengers who have been upgraded retain their underlying fare class for all other purposes (mileage earning, ticket changes, waitlist priority, etc) but they are able to utilize first class baggage allowances. I understand the OP's confusion and I don't think we will have an answer until we get some reports from pax.