So, I found how to fix it. The problem isn't in the dictionary; it's in Firefox refusing to un-Americanise itself. Solution:
Download Agent Ransack. You need this to search for files properly. Search the term "dictionaries:. You'll find a few folders with that name. One of them will contain only US English files ( en-US.aff and en-US.dic ) if your Firefox refused to use the Australian dictionary. For me the folder was C:\Program Files (x86)\Comodo\IceDragon because that's the version of Firefox I was trying to fix. Open the folder.
Also open the folder that DOES contain your Australian dictionary files ( en-AU.aff and en-AU.dic ). For me that was in an extensions folder, among other places.
Now, copy your Australian dictionary files into the folder containing your American files. Almost finished.
Next, to be sure, rename your American files. I added .was to give them a new file extension that would be easy to reverse if necessary.
NOTE: You'll need administrator access to move the files. You'll need to have file extensions visible (set that in Folder Options control panel).
Appalling. I have no idea why this exists. It can't even get simple EUROPEAN spelling of words such as Favour/Favourite, colourful (DESPITE THOSE BEING IN THE FRIGGING DESCRIPTION!!!) or even BLOODY METRE CORRECT!
I am completely flabbergasted that this exists. It is entirely useless, and clearly all of the reviews have come from people that are ENTIRELY ILLITERATE.
I'm certain that this was uploaded as a joke. GAOL <- EFFING RED LINED! ARE YOU KIDDING ME?!?!?!?!
Ultimate test: Aluminium. Can you guess if it got red lined or not?
Why is this not a Firefox language by default?这个评论是针对附加组件的一个早期版本的（2.2）。
This is great! Installed easily and quickly in a set-and-forget manner. It's great having less of those red lines! One thing though - It marks "anymore" wrong. Other than that, great!这个评论是针对附加组件的一个早期版本的（2.2）。
Installed effortlessly to Thunderbird, so glad to have a true Aussie dictionary. Thank you for your work, it's greatly appreciated :)这个评论是针对附加组件的一个早期版本的（2.2）。
This works in Fx 34 -- I edited the install RDF file to bump the Fx max version number to ensure it will install and work.
That is all that is needed to make this work for newer Fx versions
I love having this dictionary, and although it still seems to work on my old PC, even though I have updated TB to the latest 24.2, it won't let me download it on my new computer, so now I have no dictionary at all! Are you still supporting this add on? As far as I can see, you haven't updated it since 2011?这个评论是针对附加组件的一个早期版本的（2.1.2）。
No updates to the dictionary's code have been required since 2011. I have just bumped the compatibility version for TB so perhaps restart TB/FF and try again.
I've got the Australian dictionary in my number 1 slot (in preferences), British in number 2, and have removed the American dictionary, but Firefox still spellchecks my pages in US English by default. So what's the point trying to fix Firefox spelling setup with installed dictionaries?这个评论是针对附加组件的一个早期版本的（2.1.2）。
I agree with the developer completely. However, I am actually waiting for the English (British) dictionary to be ready for my Thunderbird 15. But for the time being my Australian friend will be of great help to me for my colours will not be marked red.这个评论是针对附加组件的一个早期版本的（2.1.2）。
One of my *favourite* add-ons for Firefox. The English (Australian) Dictionary prevents Australian English words being marked as incorrect. Before I had the add-on, I wasted time second-guessing my spelling because of that little wiggly, red line; even if I was certain I'd spelled a word correctly, I double-checked it every time. How annoying!! Luckily, I found this add-on, and it's been brilliant ever since. I don't have to ignore all the red wiggly lines now; it picks up my actual typos, and has saved me many times from posting incorrectly-spelled words online. I can't recommend the English (Australian) Dictionary for Firefox more highly to anyone who uses Australian English spelling.这个评论是针对附加组件的一个早期版本的（2.1.2）。
This plugin delivers exactly what it promises: a functional spell-check dictionary for Firefox. Works just fine with FF 12.0.
As an aside, I've found that this dictionary is quite a bit better for us Canadians who are used to the older Commonwealth spellings - so if you're a Canuck looking for a spell-checker that isn't rife with Americanisms, look no further.
Works for me up to FF11.0, does exactly what is says (Australian dictionary) with no issues for me.这个评论是针对附加组件的一个早期版本的（2.1.2）。
Works a treat once you figure out how to set the language. It does not use the machine set language. That had me confused for ages.
Select support for the addon for how-to
I've installed this with no issue, but it still underlines words like colour, is there some other language setting i have to set? I have the PC language set to English Australian.
This add-on is, always has been and always will be FREE. The suggested contribution is for DONATIONS. It is also bad form to write a review about a compatibility issue (being that it hasn't been updated for new versions of Thunderbird), because the add-on is not advertised to work with anything past 3.1.x.
Every part of your review reeks of poor form. Nothing is even remotely what a review is supposed to be about.
This add-on delivers EXACTLY what it promises and therefore it gets 5 stars from me, as I have read the review guidelines.
A good add-on. I gave it 4 only because I am often unable to use it because of its not being up to date with new versions.
@yanglifu90 that's your problem. I feel your "review" is null and void and would like to see it removed. If you do not understand what a "dictionary" is in WP parlance, then learn
"3. Computers .
a list of words used by a word-processing program as the standard against which to check the spelling of text entered. "
G'day Cameron, love your work. Could you please incant the spell to update the version number to support Thunderbird 8.这个评论是针对附加组件的一个早期版本的（2.1.2）。
Hi Cameron. Yeah I was debating whether to make them too high... For me, I can just reduce them as necessary just as easily as increase them so it is no big deal. What is a big deal though is that yours is tagged as the "official" EN-AU dictionary, the one that Mozilla prefers, but it is rarely up-to-date. What's going on Cameron? What are you going to do with this? Are you still supporting it or what?这个评论是针对附加组件的一个早期版本的（2.1.2）。 对这个附加组件，此用户曾发表过3个评价。
"rarely" up to date is a bit of an over dramatisation.
AMO is now automatically running tests and bumping maxversions if tests are passed for add-ons, so my trips away to the snow etc. will have less of an effect.
Big Thanks to Anywho for keeping this dictionary upgraded - most appreciated. Works perfectly
My apologies Cameron, was confused by the replies
Anywho maintains a separate packaging of this dictionary. This package hosted at https://addons.mozilla.org/en-US/firefox/addon/english-australian-dictionary/ is maintained by myself. Just clearing up any confusion :)
I have put the project on github in case anyone is interested. I have updated it to work with ff5 and tb5.
was so devoed when ff5 said no longer compatible loved not having to add aussie words to dictionary这个评论是针对附加组件的一个早期版本的（2.1.2）。