Sidebar for the community says "be wary of spoilers" but there's no mention of a rule against them. For courtesy, I'd probably keep details minimal in the title but include a warning (e.g. 'S04E20 "Episode Title" discussion [spoilers]'). There's also spoiler tag markdown that you can use to hide the details unless a user chooses to view them:

The Spoiler
I don't know, some pirate stuff.