It should be important to keep in mind what it means to spoil something. Spoil means to ruin or become rotten. Saying "Ned gets decapitated" before it happens is a spoiler. So is saying "I'm sure glad Tyrion survives the end of season 3" before it happens. Referencing something in the past could be a spoiler if it's a key point that's maybe being taken out of order in the show story line. But to say "I wish there had been pig riding" is innocuous and a "detail" that spoils neither show nor book.