You are either trading, or duping. By definition, the terms are mutually exclusive.
For example, if someone dupes you their collection and you do the same, it is not a trade dupe, as nothing is lost by either party, and therefore there is no trade. It is just duping.
The purpose of this thread is to point out that "trade duping" is a contradiction in terms, and that if you wanna dupe, just do it. Don't try to legitimize it by calling it something else.
First point: Player A and Player B each have items the other wants. Player A duplicates his items for Player B. Player B then duplicates his items for Player A. Both trading and duplicating have occurred. Items were duplicated; time was traded.
If the community refers to an action in such a way that other members of the community understand what is happening, it doesn't matter to anyone what those terms are as long as the action is understood (except grammar-nazis or people so inept at communicating that they have to resort to semantic arguments). The action could be called "sleeping" even though it has nothing to do with actually sleeping as long as people understand the reference.
Note: contrary to popular belief, I don't really care about duping. Sure, I personally consider it cheating, and think it completely defeats the point of the game, but that is irrelevant to this thread.
Second point: For someone who doesn't really care about duping, you spend A LOT of time arguing about it. Not only do you have multiple posts just in this thread, but almost every post I have seen from you is about duping.