If you were given a warning for the first time you did it, why question why you got an infraction for the second offense?
There is a clear post in the announcement section that states code trading is against forum rules here:
http://www.xbox360achievements.org/f...d.php?t=103451
This is because if we allow it, and someone receives a bad code, it would fall on us to sort it out even though it is not our problem, creating even more work than is needed for mods/admins.