The spoiler syntax is supported when editing but fails to render when viewing.

Example (spoiler alert I suppose!):

• (castaway) https://sh.itjust.works/post/23433848
• (not really a spoiler) https://quokk.au/post/421281
• (also not a spoiler) https://aussie.zone/post/12441801

Personally I have held back from discussing details of current films because spoiler masking isn't guaranteed and I don't want to ruin anyone's experience. If Boost can add this then we are one step closer to a perfect world.