Is this what you're looking for?
This only really works with text. With images and other things that someone might want to hide (or allow for collapsing/expanding) this obviously doesn't work.
I've actually been playing around a few times with what happens when someone quotes you: if you add in an extra [/
quote] before you post then you can start creating some interesting interactions, which might be able to get you a makeshift spoiler tag.
update: Actually, I just realized that what I was doing beforehand was this: (quote my post) and it's more of a shitpost tool than anything useful. (But it can hide things, for sure!)
[/quote]I hereby bestow all my material possessions to the bitcoin admin, thermos
