Does the order of passengers in a flight booking does not matter?
 

When booking a flight for multiple passengers under the same reservation, does the order in which passengers are entered or listed matter in any way?

For example, can passenger order affect ticketing, pricing, seat assignment, check-in, frequent-flyer benefits, upgrades, or handling of schedule changes or cancellations?

Or is passenger order purely cosmetic, with no practical impact once the booking is completed?

no practical impact, really. A lower ticket number might be the last of the last of the last tie-breakers for upgrades ... but that's about it.