I suppose one could find interpretive room as to whether trading constitutes bartering. However, for your information:

As found on the Forum Title for :The Coupon Connection

The exchange forum for legally transferable coupons issued by various frequent traveler programs (these include free car rental days, 50 percent off hotel stays and upgrade coupons). This is N-O-T a forum for anything related to the buying, selling or bartering of airline awards. All exchange as a result of this forum are based upon free issuance and community spirit.