From
http://forums.worldofwarcraft.com/thread.html?topicId=32274156&sid=1
There was new functionality for quest abandoning added in 1.12.1 that will destroy any items related to the quest as soon as it is abandoned. The note for this didn’t make it in time for the patch, and we’re currently in the process of approving the final revision for the web notes.
This was mainly done to curb some of the experience hording for this expansion, and any future expansions to come. We want to ensure people are leveling at an appropriate pace and not using quests which were not initially designed with an expansion in mind to move past 61-70 levels as quickly as possible. This is one of a few steps to attempt to limit the benefit players will receive from planning level progression through pre-expansion quests and turn-ins.