I'm talking about a slightly higher level of conversation structure. The features you're describing are certainly significant in how they affect spoken language (modern French is very drastically different from written French, BTW; it's very weird), but are less likely to predominate in written text like Facebook posts. This is especially the case for other samples studied by the researchers, like comments left on CNN articles. Professionally-written text is just generally well-organized; concepts and events are introduced in an efficient manner, using consistent and correct word choice. Even if the sentence structure is more familiar, when people blunder through recounting an event, we have to do more work to reconstruct what they're saying. Professional writing is composed with the benefit of hindsight and more thoughtful analysis.
...however, the researchers believe that people are just natural gossips. With that in mind, it could easily be about the density of opinions and moods in the text that makes the snippets easier to remember; the emotions of the author provide another anchor to build an associative memory around.
Carbon. He's going carbon.
OR: we switched to a case-insensitive universe while you weren't looking. Something something no one ever got fired for buying Microsoft.
User hostile.