Why are positive but controversial comments fine, but negative but controversial comments bad? Why is what's positive and negative defined solely in relation to the thread being posted in?
What if Vladimir Putin had a heart attack and dropped dead tomorrow. Certainly, that would be far more historically consequential than the death of the Queen. It would therefore have even better claim to being posted on HN.
Would you only allow positive comments on that thread? Comments that eulogized Putin as an emblem of stability and moral authority? Would you freeze or delete any comments that questioned that response?
I say this not to be facetious. It's a more extreme example, but I don't think it's qualitatively different. Clearly, it doesn't make sense to allow only positive comments regardless of the subject. When it's highly ideological and contested - as is true of both Putin and the Queen - that just arbitrarily empowers one side of the debate and infuriates and alienates the other half.
I honestly think the only fair response - short of superhuman feats of moderation - is to delete the thread.