It depends. Sometimes it may happen that the discussion goes in a wrong direction even after OP has made the made purchase...examples why AMD, Nvidia should be better and then something against is posted...so on. Believe me, I've seen several cases like that.
The Thread you're talking about, that is for OP to select his card and after lots of discussion everybody including the OP has reached the same conclusion and the purchase has been made. So no point to keep that thread open, after OP requested to do so. If it was a tech discussion regrading say, the architecture of new GCN...then we shouldn't have locked the thread.. It depends upon thread to thread and no rule is possible to unify all those things. Leave the matter.
If anyone want to continue discussion on that thread he can send moderator's PM to open it. And OP has already placed order for the card. So no point of suggesting him better option. It will only make him unhappy.