I respectfully disagree that discussion of politics on HN cannot "meaningfully change or move forward the debate and is unlikely to be instructive". Indeed, I have witnessed proof that this is not so. I have seen numerous occurrences in comment threads where there has been spirited factual debate which ended up informing both sides. I have seen minds changed. I have experienced my own mind being changed.
I don't deny, of course, that there has been some...less useful discussion, as well. But I feel that overall, it has been positive.
I say this as someone whose been that spectator.