The conversation is about "black swan but good" events and white is often used as short hand for good as opposed to black being used as short hand for something bad. It's pretty obvious what he means (even if "white swan" is most commonly used to refer to predictable major events and the term "black swan" not being limited to unfavourable events) so I'm guessing you're just being mean for no reason.
I am wondering though what exactly you think "black swan event" means and why you think that since your post here makes it rather clear you don't understand what the term refers to or where it comes from either.
Black swans are not at all rare and a "black swan event" is not called that because of the rarity of black swans. It's called that because "black swan" was at one time used to refer to non-existent or impossible things in Europe then when Australia was discovered they found out black swans are actually extremely common, a very improbable event given the data available beforehand. It's the discovery of black swans that was unlikely, not black swans, and it's the unexpectedness of their discovery that is relevant to the "black swan" metaphor. [1]
If black swans were rare seeing one would not be a "black swan event" because it would be possible to predict that one could be seen, just not very often, thus not having the required characteristic of being unpredictable beforehand. So yes, despite their post being easily understandable, the person you responded to did use "white swan" incorrectly, but your correction is just plain wrong as well.
Please if you are going to be pedantic try to also actually be correct on what you're being a jerk about first.
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it's called a black swan because black swans are rare. white swans are quite common. discoveries with the impact of antibiotics are extremely rare.
what, exactly, do you think the term "black swan" means. and why do you think that?