It is a common courtesy. But on the fandom wank link some people were saying they would never say thank you for someone protecting them from spoilers, because it's no less than what's expected. If the spoiler free are going to start complaining they aren't being shown the proper consideration, well it wouldn't hurt for said people to extend the same consideration back when people are at least making an effort to warn of possible spoiler talk. I just don't think cut tags are the spoiler free by rights, it is people thinking of them and doing them a favor.

I know what you mean about not getting the episodes at the same time as everyone else. I have to d/l so I miss the initial excitement :)