Sarcasm used to be a effective and totally valid way to make a point, -I mean it was even part of basic reading/writing education when I grew up 20 years ago.
Of course you can easily overdo it but I think banning sarcasm has a significant downside and we should rather teach people to use it correctly.
Once again, this isn't about banning anything. This is about productive conversation. A value which makes HN unique out of all the internet communities.
What the commenter was doing was insinuating a conclusion based upon a straw man, so as not to be scrutinised for the underlying conclusion.
Of course you can easily overdo it but I think banning sarcasm has a significant downside and we should rather teach people to use it correctly.