I think you might have missed this part of my post:

Since both value-adding parties involved (the news site and Steemit readers) are aware of the double-spend of your “Proof of Brain,” then they can make an informed decision about how much value they want to give you. No harm, no foul — as long as everyone involved is aware of what’s going on. In practice, this just translates into letting people know when your post can also be found elsewhere.

In other words, it's like you say and it's up to the audience and what platform may like. But my point is that the audience needs to be informed.