Based on posts and discussion earlier in the thread (especially how the thread immediately died a couple days after the trailer because someone complained about book talk), I'd say the reality is reversed and there are more people than not in the thread that already have an understanding of what's happening/going to happen. It's not 2012 anymore. When GoT launched ASOIAF had sold something like 12million copies. Now it's up around 90, with A World of Ice and Fire (summary of HoD events) nearing 10 years old, Fire & Blood (HoD detailed) nearing 6. Joffrey explicitly "spoiled" (maybe-did he know what he was talking about?) one aspect in season 3 of GoT. Shireen mentions the story in broadstrokes in season 5- and season 5 extra content outlines the whole goddamn story in detail, as voiced by GOT characters in an animated featurette.
I suspect that the overlap of people that care enough about the subject matter to talk about it on a hockey message board and the people that have consumed some of the above media is kinda high, and we're no longer looking at a minority of "book readers" spoiling things for the majority as it was during the early GoT run, instead at a minority of "in the darkers" demanding that the discussion be neutered for their benefit.
In the end the board rules are the board rules, but if every insight/thought/opinion, is going to be going to be met with "iS ThAT a SPoiLEr???" it's pretty easy to see this either becoming a dead thread where 5 guys tweet about their initial reaction every Sunday, or one that is 70% spoiler tags.