It's been one of those issues the Twitterati love - because it's all about them and their beloved medium.

But the story the Twitterverse has dubbed #twitdef and #posettigate raises a host of fascinating issues - ethical, legal and practical - as the most combative of Australia's old media outlets takes on one of the most fervent advocates of the new. In the middle is a frightened and chastened middle-aged woman, who is also one of the country's most respected specialist journalists.

The 'fervent advocate' is Julie Posetti, a lecturer in journalism at the University of Canberra. What she advocates is the use of social media, and Twitter in particular, as journalistic tools. She practices what she preaches: she's one of the most prolific tweeters in Australia.

Last week she was one of several hundred people attending the annual conference of the Journalism Education Association of Australia at the University of Technology Sydney. She and her fellow journalism profs certainly got an education in how the big boys play ball.

On the second day of the conference, a panel discussed how the media has covered climate change. Both panel and audience were clearly fervent believers that climate change is real, and crucially important, and inadequately reported. There were no dissenting voices, that I've heard about (I should make it clear I was not at the conference).

One of the more revealing contributions came from the former rural affairs reporter for The Australian, Asa Wahlquist. Though well-respected in the profession, she has not been well for a long time and consequently very seldom went into The Australian's office in Holt Street, Sydney but instead worked from home. She recently resigned, and that day she told the JEAA conference one of the reasons why. What she said was recorded at the time and is now available for everyone to hear - more on that in a minute.

But last Thursday, the gist of what she said was already being broadcast. In what has become a commonplace at any conference where matters of public interest are discussed, a stream of tweets summarising and condensing what was being said was being sent out. On this occassion the tweeter was Julie Posetti.

Initially, of course, the tweets went to her 5,000 or so followers. But any one of them could retweet anything she tweeted to thousands more. And what Asa Wahlquist had to say about her former editor-in-chief, Chris Mitchell, and his attitude to climate change made for some pretty explosive tweets.

At this stage, if you haven't already done so, I suggest you read this story and listen to the appended recording of Wahlquist's remarks. I promise you both are well worth your time. But before you go, take this thought with you, because it's important to my argument:

I disagree with the ABC's transcript. Although the recording is indistinct at that point, I don't think Asa Wahlquist said: "The other thing that was happening at The Australian before I left was the editor-in-chief and the edits becoming much more prescriptive..."

I think she said: "The other thing that was happening at The Australian before I left was the editor-in-chief and the editors (were?) becoming much more prescriptive..."

Now, go, read and listen, then come back.

From The Australian's point of view, it's not pretty listening, is it? As you'll have gathered, Chris Mitchell, editor-in-chief of The Australian, denies that he ever leant on Asa Wahlquist to write her stories in a particular way, and was reported in his own newspaper last Friday as being in the process of preparing to sue Julie Posetti for defamation.

"I am not one who believes new media should be exempt from the normal laws of the land," Mitchell reportedly said.

Well, the Twitterverse immediately went incandescent. Numerous people have pointed out the hypocrisy of the editor-in-chief of The Australian resorting to the defamation laws when his own newspaper has frequently editorialised along these lines:

"Newspapers have become accustomed to being the victims of Australia's ludicrous defamation laws, which act to suppress free speech and enrich lawyers..." (Editorial, The Australian, 31 January 2004).

(In an email to me this morning, Chris Mitchell responds: "I do not believe our editorial support for defamation law reform has ever extended to supporting the right to publish outrageous lies.")

Yet for all that he's the last person who should be resorting to the lawyers, Mitchell is surely right in one thing: to use Twitter is to publish, and publications in Australia are subject to the law of defamation. And that law, in Australia, can be very restrictive indeed.

This has some serious consequences for journalists attempting to live tweet reports of contentious and potentially defamatory speeches. There is a defence in the current defamation acts in all states for the fair reporting of proceedings of a public meeting that relate to a matter of public interest. Presumably that will be the defence that Posetti will rely on.

But to gain that protection, the report must be fair and accurate. And you can bet that the lawyers for the plaintiff, if it ever comes to a court case, will be doing their darnedest to show that Julie Posetti's Tweets weren't. Despite most twitterers (and the ABC's reporter) apparently thinking the recording vindicates Posetti, I think they would have something of a case.

The essence of what Wahlquist had to say was summarised fairly enough. But in a defamation case in Australia, near enough isn't necessarily good enough.

For one example, when Posetti tweeted: "Wahlquist: 'Chris Mitchell (Oz Ed) goes down the Eco-Fascist line' on #climatechange'", she was attempting to compress into 140 characters a really complicated allegation: that Chris Mitchell agrees with those who think that belief in climate change is "a political movement that the left has now adopted that... aims to destroy everything that he loves and values". In other words, Wahlquist was saying, Mitchell believes the climate change 'alarmists' are 'eco-fascists'.

Mitchell denies that he has any such belief, and that denial couldn't be included in an instant tweet. But in any case, it would be easy for Mitchell's lawyers to show that many Twitter users took Posetti's tweet to mean that Mitchell himself is an 'eco-fascist'. They may not know what it means, but it certainly doesn't sound like a good thing to be. Calling anyone any kind of fascist is undeniably a defamatory thing to do.

Now Posetti (who on legal advice isn't commenting at the moment) can point out that she did her best to report accurately: after all, she did tweet "goes down the Eco-Fascist line", not "is an Eco-Fascist". But given the lack of context that's an inescapable part of Twitter, Mitchell's lawyers could argue view that there's a clear imputation that he is some kind of fascist - bad news for Posetti if the court accepts that argument.

Then there's that other contentious tweet: "Wahlquist: 'In the lead up to the election the Ed in Chief was increasingly telling me what to write.' It was prescriptive."

But that's not what Wahlquist said. As I wrote earlier, in my view she said: "the editor-in-chief and the editors were becoming much more prescriptive and you saw that in the lead-up to the election, where you were actually being told what to write."

She did not say that Mitchell ever spoke to her directly, or told her what to write. She implied that he laid down a line that his editors ensured that everyone at the paper followed.

Asked by me if he had any comment on Asa's recorded remarks, Chris Mitchell emailed me this morning:

"Some facts: Asa was not a science or environment writer and did not file about climate change. She did not file on climate change issues before the election according to our news desk... I have an extensive and grateful resignation letter from her in which she is personally thankful to me and asks for a continuing relationship as a contributor filing features in her specialist area of rural affairs. Until last week Asa had not spoken to or emailed me and neither I her since 2003."

I put these comments to Asa Wahlquist, who, understandably, declined to respond on the record. But a search in Factiva for 'climate change' and 'Asa Wahlquist' produces some 300 returns, the majority of them reports in The Australian - including one about the value of soil carbon to farmers, written during the election campaign. And to claim that the author of a book called Thirsty Country, and the winner of the prestigious Peter Hunt Eureka Award for Environmental Journalism, is not a science or environment writer stretches credulity a bit.

In any case, the fact (which Wahlquist has reportedly confirmed) that Mitchell and she haven't spoken to each other for years doesn't mean that what she actually said at the JEAA Conference is false. It does mean that what Posetti tweeted was wrong.

Oh, semantics, mere quibbles, you may say. But any journalist and any media lawyer knows the castles of doubt and derision that a skilled barrister can build on such quibbles. If you want to win defamation battles, you need to get these things right. And the courts are remarkably intolerant of journalists who say, "But your honour, I didn't have time before my deadline".

That's why live tweeting is such a dangerous journalistic endeavour. There's no chance for a second eye on your copy, no chance to give the person defamed an opportunity to defend themselves, no space to make clear the context, no room for elaboration, and no time to run it past the lawyers - and yet your tweets can reach thousands, and sometimes (as in this case) hundreds of thousands.

But that's where the second lesson of this affair needs to be learnt - and this lesson is surely for Chris Mitchell. Because had it not been for his actions, Posetti's tweets are unlikely to have reached more than a few thousand people.

But the report in his own newspaper of his threat to sue a journalism lecturer included at least one of the allegedly defamatory tweets. And that threat then went global on Twitter, and greatly magnified any damage the original tweet might have done to his reputation.

For example, New York University media professor and new media guru Jay Rosen (@jayrosen_nyu) has jumped into the fray. Last Friday he put out a tweet linking to Crikey's report of the affair, with the comment:

Q. What newspaper has ever revealed itself to be such a threat to freedom of the press as The Australian has in #twitdef ?

Rosen has about 46,000 followers, including journalists all over the world. I'm prepared to bet that very few of them have a greater admiration for The Australian or its editor-in-chief than they would have done before this story went viral.

But Mitchell would be hard-pressed to argue that most of that damage to his reputation would ever have been caused, if he hadn't threatened to sue Julie Posetti.

I put this point to Mitchell too, but he had no comment to make.

At Media Watch, we're well aware that The Australian reacts to criticism or challenge with a vitriol unmatched elsewhere in the Australia media. But surely Chris Mitchell - who whatever else he is, is no fool - will realise that pursuing Ms Posetti through the courts (and incidentally risking some devastating evidence from Asa Wahlquist and, perhaps, other former and current staffers at The Oz, if they chose to risk speaking out) will not be in his interest, or The Australian's; and it certainly won't foster "freedom of speech and a vigorous and open marketplace of ideas" which, as The Australian argued in an editorial in 2004, "are essential to a democratic society".

Jonathan Holmes is the presenter of ABC TV's Media Watch.