You wouldn't give up ownership -- anything you create is still yours and you own the copyright. However, I'm not sure if everyone realizes that posting a story on a public forum means giving up most of your rights to submit it for publication later (like in a short story contest or a magazine).
The easy solution is this -- if you want to keep first publishing rights, post it somewhere private (Quip, Evernote, Google Docs, etc.) and PM people the private link. Or just post it in a private message within Discuss -- you can add multiple users to the same private-message thread easily, so that would work like a charm.
It would take away from the open sharing & learning community aspect, but in the spirit of openness, maybe everyone should be free to make their own choice.