Good point. Where is the line? It will be difficult to draw one.

In my comment above, I mentioned how this problem is not only technical, but ethical as well. You seem to be picking up on the same idea in your comment.

Maybe we have to use our own discretion in the examples you provided. We of course know that a straight copy/paste of an old post seems ridiculous, and we have to begin to make our own ethical considerations as we walk back from the most flagrant abuses of the system.

Overall, I feel there is little issue with re-purposing when you have put effort into reworking the piece into something "original" again.