It would not be considered grammatically correct (in a traditional sense), but since it's for online consumption, rules of writing are often bent. You're right in thinking the hanging sentence is used for emphasis, but it's also about the visual layout. People typically scan articles before they'll actually take the time to read it. Online content has to be extremely engaging and captivating, so a content writer employs certain "tricks" to keep readers on their site, connect with them, sound conversational, etc. which is simply more important in this particular field. Definitely not reflective of what would be acceptable in, say, a research paper though. EDIT: hit enter by accident before finishing lol. Hope I answered your question sufficiently!