University of Warwick suspends 11 students over rape jokes

I think liability to punishment depends on whether publication was reasonably foreseeable ie an objective test. The level of punishment should depend on actual foresight ie a subjective test and actual and potential harm caused with a leaning towards actual harm.

Perhaps you're right that it would be treated this way by the courts, though I have some doubts about its usefulness. It would mean that only people who are entirely sure that their comments would not be shared would be safe (breach of confidence would be unforeseeable (usually), but what about where you might foresee something equivalent to whistle-blowing (even if it does not meet the public interest test)?).

Also say you make rape comments quite seriously, tell your friend to send them to the victim of the comments, and realise there is maybe a 50/50 chance they will send the comments, that would be as culpable as the Warwick case where there is a very high likelihood that the comments would not be shared with third parties. After all, there are millions of chats like this in the world (which are hugely embarrassing to the participants), and only 10 or so have been outed to the press in this way.

I don't think that stuffy old judges, who don't truly understand social media and would be shocked if someone burped without excusing themselves, can be trusted to determine what is reasonable behaviour in the modern age. E.g. R v Brown.

I don't think you are right about the "very high". I think in both the Warwick and the Exeter cases, what you have a large groups of students with no real shared ideology and little personal loyalty. The Exeter group might have started as a tightly knit group of friends but it clearly expanded as the message board became used for law society communications. It looks as though the Warwick group started large. If the group was threatening to cut off members' tongues between the low and high water marks, then betrayal might be understandable, but membership of these groups were available for the asking.

Judges, like most professions, are communicating privately electronically and they are very clear about what is and what is not in the public domain.