We now have spoiler tags!
(to reveal: hover over the black bar on desktop or click on it on mobile/tablet)
To use them just wrap your text in [sp] tags.
Examples:
(replacing the curly brackets { } with square ones [ ])
a spoiler without description:
{sp}Darth Vader is Luke's father{/sp}
Darth Vader is Luke's father
a spoiler with description:
{sp="Star Wars episode 5 spoiler"}Darth Vader is Luke's father{/sp}
Star Wars episode 5 spoiler: Darth Vader is Luke's father