Although I do not find anything odd about the clothing on this person (might be considered NSFW), I find it surprising that a pilot can ask a passenger to change their clothes before letting them on.
What are some of the definitive examples of inappropriate clothing when flying (keeping aside the obvious choices of travelling in undergarments, T-Shirts displaying controversial political/religious beliefs) that can make the pilot/crew ask me to change ?
I think you have covered all the typical reasons; I would also avoid T-Shirts with images of guns, explosives, etc. The link you shared with a woman with very short shorts could be seen by some as underwear. But back in the day, Southwest Airlines in the United States used to have their "Stewardesses" wear hot-pants.
That depends on the cultural background of the country you are flying (from and to), and how relatively conservative or liberal the decision maker is.
Generally, if it gets you in a good restaurant (in that country), you will have no problems on the airplane.
Edit: I should have said 'medium level restaurant', I didn't mean 'upscale', just not 'cheapo' either
It is easier to answer the question the way you worded it than the other way around. Finding a list of items that will get you kicked out of a plane probably depends on local customs and the pilot's mood!
What will not have you kicked out of a plane is easier. For men, trousers without holes which cover entirely undergarments. A woman can wear pants too but long skirts are acceptable. In many places one can go shorter but if you are connecting through some more religious countries, keep it below the knees.
Wearing a top which covers your upper body, including the shoulders also not get you kicked off the plane unless it is transparent or features offensive words or imagery. Even if you transit through some country where women cover their hair, a tourist is rarely asked to do with on the plane or in the airport.
As for examples that will get out. This will vary greatly, if you take a charter flight to beach destinations for example, you will often see people in shorts and bikini tops. In many other I areas, I suspect this be enough to get kicked out. Very shear materials or belly-tops are also likely to be frowned upon.
It's not a rule on paper that decides what's allowed, it's a human with their own history and beliefs who has that authority - if you can't board the flight it doesn't exactly help you that the airline apologizes to you afterwards because the decision to throw you off was clearly wrong.
People get thrown off flights for the most ridiculous reasons, so my personal advice is: Dress like you always do, don't bother with the small chance that you'll meet someone wanting to abuse their power, and if bad luck hits you, revel in the fact that you now have a good story to tell, while the power-tripping simpleton who threw you off the plane is probably getting fired for it.
If you want to be more specific:
There are a wide variety of reasons why you may be denied boarding. I described some of the alleged security reasons here with references: Physical appearance and clothing, do they affect the passenger's chances of getting on the plane?
In the example in question, the reason was not security (or a pretence at security), it was (allegedly) decency. From the article:
The airline’s policy states that they have the right to remove anyone from a flight ‘whose clothing is lewd, obscene, or patently offensive’.
Personally I don't think the clothing is 'lewd', 'obscene' or 'patently offensive', but it's not up to me. The airline in essence has the right to deny boarding for any reason; if you ask on avation.se they will tell you the pilot will make the final call. I would expect that if you flew with an Iranian carrier, the standards they would apply would differ substantially from (e.g.) a Swedish carrier. I think your quest for 'definitive examples' is not going to be fruitful, as this is a judgment call. However, the link above will take you to some ridiculous decisions.
It is illegal for civilians to wear camouflage clothing in Trinidad & Tobago, so if you're heading that way you should avoid wearing clothing (or carrying luggage) that features any camouflage patterns.
When I flew there (from the UK) last year we were advised that we would not be allowed to board our flight if were so attired.
Temperature in Boston, MA on 2016-05-25: 88F (31°C).
Temperature in Seattle, WA on 2016-05-25: 66F (19°C).
Sudden changes in temperature can make a person sick. The pilot was simply trying to protect this young woman's health by suggesting she cover up with appropriate clothing.
Thus, to answer your question: Wear clothing suitable for the destination's weather and it won't be an issue.
australiatag? The flight in question was in the US.