So, Munsu, whatīs the argument against spoiler tags? I must have been absent when that was discussed.

From how you worded it above, I think youīre taking the "spoiler-tags" name too literal. We donīt want spoiler-tags so we can freely talk about actual spoilers, like talking about what happens in Attack on Titan after the anime-end. Rather, we want those spoiler-tags as a comfortable, quick tool to hide text that not everybody necessarily wants to see. Preview talk is the main reason here. Another example, and extremely common in other boards, is when youīre talking about a videogame. When a new title has been released, "itīs all out". But it is common courtesy not to talk freely about plot points or surprising/fun character scenes, because other player might not yet have reached that point in the game. So you use spoiler-tags, even though you could argue that everything is out in the public and thus naturally "not a spoiler".

So, my argument would be that talking about previews in anime is the same as talking about mid-to-late content in a videogame. Itīs polite not spoil it, even though it technically cannot be called spoiler. Therefore spoiler tags.