I always err on the side of "it's a spoiler". If it's not in the show's trailer, I treat it like a spoiler.

I know that I'm personally much more sensitive to spoilers than a lot of other people, so it always annoys me how somebody says something thinking they're not spoiling anything without fully thinking through the implications of what it is they're saying. It's almost arrogance, really, to simply assume that you know what will and will not spoil some given experience for another person.