Uh, I'm getting confused by this lengthy discussion with that many sideshows. Now I get it. You're perfectly right with that. What happened in this case by the user is not really(*) covered by those paragraphs. This is about "Persönlichkeitsrecht" (personal/privacy rights), maybe including a sideshow with copyright. But this is way more nuanced and requires looking at the details. People have a right not to be doxxed or their secrets or private stuff being publicised. But as you said, there isn't a general rule to prohibit sharing documents itself, without fail (like we have for audio recordings). With written text, a court needs to look at the actual content and see whether that's protected or private in some way. Because privacy is protected in itself, and in that case it's not about the form of a document.

Edit: And to add to this: I think §201a still applies. Someones Inbox or DMs count as a private/protected space. Now if you take screenshots from that, that's an "other images". And the fifth subsection says these can't be shared with a third party.