For what it's worth, if you post a story (for example) to the open internet -- your blog, social media -- and there is NOT a paywall or explicitly restricted access, many (if not all) publishers will consider that material previously published. That doesn't mean it's public domain at all, but it does recognize that the work is not private. Likewise, I'd consider any social media post being akin to posting a sign in my front yard. If someone does the work of driving by and taking pictures of the signs in my front lawn, that's their right -- unless I'm in a closed, gated community.

Then again, i see people thinking that they somehow "own" their Facebook feed, so ....