Sith.....yes, almost...except the actual heading of this thread.

The same applies with 'incitement to riot'.  There does NOT actually have to be a riot occur.

If one looks closely into 'Laws' you'll find some interesting ones.  The might seem 'absurd' but they exist for a reason...

That all depends on determining whether an apparent 'statement of intent' is an actual crime in itself. [I think you'll find that it is].

You do not have to light a fire first to have the shout of 'Fire!' in an auditorium be deemed a criminal act.

Your 'personal definition' is all very well but does not necessarily bear any relevance with actuality.

Do you have to demonstrate 'intent' to cause panic... or simply act/do something sufficiently irresponsible to achieve the same effect?

At the end of the day, 'intent' [or not] does not matter if the potential repercussions are the same.

It is Law Enforcement's first and most important job to ensure public safety. Therefore, the young man was found and arrested. Efficiently and without him being harmed during the process. No one was overzealous. An "Abundance of caution" was exercised, and rather well. Kudos to all involved.

Context is everything:

If you're on the street and see a long lost friend named Jack and yell, "Hi Jack!", nothing untoward will happen.

On the other hand:

If you're at the airport to pick up a friend named Jack whom you haven't seen in a long while, just yell, "Hi, Jack!" and make sure to wave your arms. You will be arrested. 

But it was not his intent, which is why it is clear that no crime has been committed.

Well, that's why I was very clear about saying it was my definition. I mostly wanted to layout where I thought such a charge should fall, regardless of how it is currently acted upon. Heck, if the definition of terrorism was saying the word 'bomb' in public (arrests and all still happen), I would be saying the same thing. In that case, the law should change because it is wrong. The trouble with a terrorism charge is that there really isn't a clear definition. That's wrong too. It needs to be clearly defined.

Clearly my definition wasn't a legal definition, but if I were to pretend it was... You're suggesting a case where someone clearly did/intended to kill civilians in a public format, but it is not clear whether they were/intended to cause public panic? Not a very likely case, I'd say. But, yes... in that case a certain recklessness on the part of the killer regarding public panic could be construed as terrorism. That would be for a jury to decide. Along with all the clear evidence of murder.

Really because everyday billions of people get in their cars to go to work or go home. Car accidents kill more people than anything else that jumps to mind at the moment. You're saying they should all be arrested because even though it isn't their 'intent' to kill someone, and even though they didn't kill anyone, they might? What about climate change? Scientists say that if everything continues, there could be affects years from now that cause deaths (severe weather, floods, droughts).... so all those people should also be arrested for also causing deaths of people that haven't even been born yet? Those mass murders! Lock them all up! Oh wait, we already lock up more people than any other country by a lot.

However, what I have read from your post suggests you think it's possible for someone to 'accidentally' be a terrorist. Not by not paying attention to who you sell weapons, fertilizer, give money to, but by saying the wrong things in the wrong place. I am 100% against this. You yourself pointed out the separate charge of 'incitement to riot'. Why have 2 charges for the same thing if both mean 'your negligence almost caused panic'?
If some drunk pilot crashed into another skyscraper, causing the same circumstances as 9/11, they are not a terrorist. Yes, they have to face the consequences of their actions. It's like murder. You can't 'accidentally' murder someone. If it's accidental, it's manslaughter. If it's not, it's murder. No, everything isn't black and white. The story in the OP is clearly white.

Words are only circumstantial (as pointed about by everyone who used the word 'context' in this post). I am also against bringing charges against anyone with only circumstantial evidence. I also believe the more severe the charge, the more solid the evidence must be. Especially now that story about the NSA recording all phone conversations, text messages and whatnot broke. 

Again, I am not saying he should not have been taken away from there as 'an abundance of caution'. The 'over-zealousness' was actually charging him with anything when they have no evidence against him. That is my point of contention.

They have the evidence.  He tweeted...and admitted to doing so.

In that respect it's a 'smoking gun'....with his fingerprints on it...and it's still in his hand.

OK, he didn't hit anyone with it...but he did 'discharge the firearm' in a public place.

Yes, I know it's an analogy...but unarguably a valid one.

And adding to that, he could have been sitting at home and tweeting the same thing and there'd be no response - no justification for action.

Again, it's about context...about the circumstances of where it occured.

When a statement you make has the potential to be construed as a statement of intent to perform a terrorist act you will find yourself responded to as if that is truly the case.  To respond otherwise is to expose yourself to a charge of criminal negligence.

How the courts deal with this particular incident should be enlightening.... and likely a sobering wake-up call to the naive....

Yep...and with criminal charges comes the whole ruination of his future.

Like I said in the OP title.

i hope that would come with convictions, not charges.

do public nuisance offenses show up on a criminal record one needs for job applications in Australia? because no amount of wishful thinking will lead to "charges of terrorism".

they must have realised that this was bogus before they put the transcripts on the internet

i was in the U.S. twice. nice hospitable people, great landscapes, horrible food. but i really wouldn't consider my life ruined if i wouldn't have been there.

is it really that much harder to travel for Australians than Europeans? i don't think so. i have had to apply for visa in quite a few countries and none of them ever wanted to see a criminal record (the US didn't as well back then if i remember correctly).

personally i think there might not even be a conviction. be it as it may, next week i will have forgotten about it anyways. and in the meantime the Syrian Army will take care about the real terrorists from Australia. link

wouldn't make sense to ask for a criminal record for permanent immigration then. also i refuse to believe that the visa-on-arrival guy at some airport has access to my homecountry's databases. i'm not that paranoid yet.

there might be a rare case scenario that one government might ask for a criminal record from an other, but i still hope that this kind of information isn't handed over so easily. the US is an exception in this case.

do you know what visa-on-arrival means? in many countries as a EU-citizen (and probably as US- or Australian citizen as well) you do apply for the visa at the immigration counter at the airport or border on arrival. 

there are countries that require a visa (like India, the US, Russia or Iran) before entering.

and no, handing out information like criminal records to foreign nations without your consent would be illegal here. i think the US makes that consent mandatory for application now. It did not in 1995 when i was there the last time. India, Russia and Iran did not. (and all those countries were in recent years)