In general, newspapers have taken the view that if people sit in the pub, read headlines and/or articles and then discuss them that the content of that discussion is entirely outside the responsibility of the newspaper. That has been tempered with laws, rules and regulations that cover inflammatory content of one kind or another but so long as the original article stays within the lines of the permissible (no matter how close it comes), the view has held pretty much intact for generations. But if the article is on the internet and the discussion is not within a handful of people muttering into their beer but is available to the entire connected world, and the means of making that discussion available is owned and operated and controlled by the newspaper, is that a material difference? An English court decision is opening the door for it to be so and the ultimate consequence could be full responsibility for all on-line publishers including social media.
