What are the twenty worst mistakes to make when writing Australian English if you have never visited nor understand Australia?

Based on my experience having lived in both England and Australia, and having many North American business communicators as friends, the 20 worst mistakes to make when writing Australian English if you have never visited nor understand Australia are:

1. Using “-ize” or “-yze” endings instead of “-ise” and “-yse” (e.g. “realize” instead of “realise”, “analyze” instead of “analyse”)[1][3]
2. Using “-or” endings instead of “-our” (e.g. “color” instead of “colour”, “honor” instead of “honour”)[1][3][5]
3. Using “-er” endings instead of “-re” (e.g. “center” instead of “centre”, “theater” instead of “theatre”)[1][3][5]
4. Confusing “disinterested” (unbiased) with “uninterested” (unconcerned)[1]
5. Confusing “discreet” (careful, private) with “discrete” (distinct)[1]
6. Confusing “dependant” (person relying on another) with “dependent” (conditional on)[1]
7. Confusing “complement” (complete) with “compliment” (praise)[1]
8. Using American spellings like “judgment” instead of the Australian “judgement”[3][4]
9. Using American spellings like “labor” instead of the Australian “labour”[3]
10. Using American spellings like “theater” instead of the Australian “theatre”[3]
11. Using American spellings like “toward” instead of the Australian “towards”[3]
12. Using American double quotation marks instead of the Australian single quotation marks[3]
13. Placing punctuation inside quotation marks instead of outside, as is standard in Australian English[3]
14. Not using the serial comma (the comma before “and” in a list) which is not used in Australian English[3]
15. Mixing American and Australian spellings within the same document[5]
16. Not using an Australian English dictionary as the primary reference for spelling[4]
17. Not following the specific spelling guidance provided in style manuals like the Australian Government Style Manual[4]
18. Not accounting for changes in word spellings over time and using an outdated dictionary[4]
19. Not using specialist dictionaries for technical or scientific writing[4]
20. Assuming there is always a single “correct” spelling when English has many regional variations[4]

Further reading:

[1] https://wordsofworth.org/au/articles/common-australian-english-misspellings/
[2] https://www.youtube.com/watch?v=d7vQ5nGKDg8
[3] https://www.eliteediting.com.au/avoiding-americanisms-when-using-australianbritish-english/
[4] https://www.stylemanual.gov.au/grammar-punctuation-and-conventions/spelling
[5] https://davidbrewsterwriter.com/blog/2014/1/14/color-or-colour-are-you-writing-your-english-right