Why would the user be able to sue? Unless they thought their work was being infringed (in which case why they wouldn’t send a dmca?) I don’t see what possible standing they’d have.

Make sure your posts are deleted, and sell it to an advertiser. Just look up where to sell. A 13 Year old account will make you a good bit of money, and it will in all likelihood be used to spam the site with an ad campaign.