Whoever wins that amount I hope he can post here and verify the winning I'm not comfortable that the owner or representative is the one posting it here, although there is nothing wrong with it.
If the winner have an account here why not, but i don't think he will or so. If the screenshot is posted by OP is the winner's profile history page, he probably a huge bettor, considering he was just lost $7k bet and the win is just a normal win to him. Its just that it was the highest recorded win in the platform as for OP but who knows.
I was thinking about that: if the winner has an account in Bitcointalk, chances are that he won't want to be known for it, multiplying the attack vectors after being targeted as a highly probable wealthy person (no poor man bets so heavily). On the contrary, if he posted from a brand new account, how can we be sure that it was not posted by some impersonator or the OP himself?
We will have to live with the doubt. I personally tend to believe in these stories (call me naive, but chances to win national lottery are much lower and this still happens), but they alone are not enough to convince me to gamble in any certain platform.