I think allowing users to subtract points leads to a larger delta between good and bad content leading to a better differentiation and ranking of content insofar as voters are good judges. I think this is mathematically unassailable.

All that's left to discuss is strategies for maximizing the quality of votes and voters. Ex minimizing the impact of low quality voters by requiring rep to vote.

I think highly paid professionals whose wages mostly put them in the top 10% of the world have an easier time changing tech support forums, perhaps by opening a new tab, than the refugees fleeing murder and mayhem with nothing but the clothes on their backs have of picking a different country to land in.

Perhaps pick a less disgusting comparison.