Yes, the law is stupid isn't it.
Is there actually a law stating you can't discuss unaired material in the UK?
I'd be massively shocked if this was the case, as one simple sentence in google can get me full episode reviews/synopsis'.
You can't police where and how somebody learnt information integral to an episode of television, whether they Torrented, Newsgrouped or watched a stream from a website or actually just read about it on one of the many episode review blogs.
I don't personally get it, yes this is a UK forum, but you can't realistically expect people to avoid discussion on a discussion forum because some people might not like spoilers, the tags are there. And as has been pointed out, we do have member's who live in america, so any 'law' pertaining to the discussion wouldn't be valid for them...
it's too vague and messy to police such an open discussion thread, Simply asking people to tag the spoilers is easier, and those who don't want to randomly fall on them, just don't open. Simple.