Well, here I am, not on either side...
But I don't believe that those screenshots provided much evidence in the way of things and is very in sync with the story that you're giving us.
Now, I'm not a friend of Merceless, so my opinion is completely unbiased. I just think that next time, you should take a couple more screen shots. :c
I don't buy or sell MS anymore unless I can gather my guild and I refuse to negotiate in whisper.
I make sure that I can talk to them in an open are so all can see what the other is saying. Though it is hard to prove that someone didn't pay you without evidence unless you can catch them saying, "No, I'm not paying you."
Even so, if you truly were scammed, I am sorry for you loss.
If you weren't, well, I implore you to stop trying to convince people that someone is a scammer when they are not. :c