If you click the question mark icon at the far right of the markdown buttons when in the comment editor it should take you to documentation for the markdown.
::: spoiler This is the displayed text.
This content
Is hidden, can put images and everything here
:::
I don't think any mobile apps actually support this spoiler syntax though.
Look between the two blondes at hip height. There's a guy peaking through. Most the times this meme was about someone being hidden in the photo. Unfortunately many are people of color who didn't show up well in photos with poor lighting