Dabees, no legal precedent has been set. Prosecutions under the Telecommunications Act and Communciations Act happen all the time. It seems to be a big fallacy that you can say what you like on the internet without fear of reproach. That is not so, it is just more difficult to deal with because of the anonymity aspect.
Some of what I see on here would easily fall under the definitions in those acts and in fact exceed them. I am appalled that some of the things that are said are allowed to remain. I do not think the Ed and her team could be culpable though because of the disclaimers everywhere and the
Site Rules. However, if a particular comment was brought to their attention and then left, I wonder if that might form a case for assisting an offender.
I have personal (not professional) experience of this. On another site in response to a very innocuous message I sent, I received an extremely menacing response, which made me feel awful. I reported it to the police. The website owners (eventually) gave them the poster's details and he was traced. The case is now taking its normal course.