Since they specifically point out back-end state and full page reloads as an option, they're clearly asking from a place of incredulity. As in, "Wait, HNers actually think this is good UX?"

And no, moving client-side logic to the back-end isn't self-evidently superior. Not for your implementation nor for user UX. So you'd have to use more than condescension to make your point. Full page reloads for an "Add Row" button died for more reasons than just "web developers are idiots and don't realize how everyone actually loved that."