First of all, it's about an entrepreneur traveling to the US for a startup, which is directly relevant to a significant proportion of YCombinator founders themselves.
Beyond its direct relevance to the core founding audience of HN, it is not clickbait or wantonly inflammatory, and is clearly of interest to many based on the comment activity and votes.
Have you read this discussion? It was already heated, although the comments posted recently have been better.
Before greggyb asked why it was flagged, the top comments were about "the dumbest bully from their grade school" and "team grade school bullies". Does that not sound like flag-worthy discussion to you?
Name calling like that buries legitimate discussion, like the claim that she was not in fact eligible for a TN visa because she "worked for" a startup she co-founded (Holy! Water).
"NAFTA specifically prohibits self-employment for TN visa holders. This restriction poses challenges for entrepreneurs who wish to start a business in the United States."
https://www.visapro.com/resources/article/tn-visa-to-green-c...