Communication Act 2003 wrote:(2)A person is guilty of an offence if, for the purpose of causing annoyance, inconvenience or needless anxiety to another, he—
(a)sends by means of a public electronic communications network, a message that he knows to be false,
(b)causes such a message to be sent; or
(c)persistently makes use of a public electronic communications network.
Seems to suggest that an annoying bit of sarcasm posted on t'internet might be a criminal offence...