Doesn't stop you from making a labeled non-spoiler thread. Although, since all promotional materials are spoilers for non-aired episodes, it doesn't make sense to start a non-spoiler thread until there are aired episodes to discuss.
As for Ned, if he doesn't meet his end, that's a deviation that would destroy pretty much the entire series. As source material they'd have to basically throw out the rest of the books. I suppose they could do that, and they might retain new viewers, but I can't think of a single fan of the books who would want to watch knowing that it would be so radically different.