Really. From your source (the Reason article):
"On 19 December 2012, to strike a balance between freedom of speech and criminality, the
Director of Public Prosecutions issued interim guidelines, clarifying when social messaging is eligible for criminal prosecution under UK law. Only communications that are credible threats of violence, harassment, or
stalking (such as aggressive
Internet trolling) which specifically targets an individual or individuals, or breaches a
court order designed to protect someone (such as those protecting the identity of a victim of a sexual offence) will be prosecuted. Communications that express an "unpopular or unfashionable opinion about serious or trivial matters, or banter or humour, even if distasteful to some and painful to those subjected to it" will not. Communications that are merely "grossly offensive, indecent, obscene or false" will be prosecuted only when it can be shown to be necessary and proportionate."
As far as I'm aware, the anti-monarchists were later released without any charges.