What a weird and unwieldy spoiler syntax, I wonder where Lemmy grabbed that from. Specifically, the tag start condition is ::: spoiler, which doesn’t match any markdown syntax I’ve ever seen, it requires having a title, and it doesn’t work in the middle of a line at all, you have to make it an entire block.

So instead of The sky is >!blue!< and not green or something like that, you have to write:

The sky is
::: spoiler this spoiler title part is required
blue
::: 
and not green

The sky is

and not green