Something I learned from this thread: that baggage allowance is part of the reservation record. In all my years of flying (and reading FT), I've never run into this. I always assumed it was based on the operating carrier's policy in combination with the fare class of the ticket, not with anything specific in the reservation (other than fare class). I do think that errors with this occur more than most of us realize, and that in most cases, common sense and experience is applied to the situation by the check-in staff such that we're never aware of it.