I meant the precedent of wherever he'd be able to get royalties for something he wrote on a social media website.
you're giving full copyright to the social media website you're posting on. If someone wanted to buy a licence to use this - whatever it might be - the discussion would be between the social media platform and the licensee.
the original author of the work would not have any stake in that theoretical situation.
If you were wondering which specific case I'm referring to, ForHackernews linked to the wiki article. there is a small note on the licensing issue at the end there.
https://news.ycombinator.com/item?id=42509955
From what I remember, he had gotten a WB offer - which ultimately didn't pan out because a licensing agreeming couldn't occur. He'd have had to rewrite the story off-reddit for them to be able to license it. And that never happened.
(Well, he did rewrite it - but probably took too long, so the window of opportunity had already closed and it was never made into an actual movie)