This is not really an issue of whether prices can go negative though. It'ss whether IB supported negative prices, and whilst it's true the drop happened quickly

This is not really an issue of whether prices can go negative though. It'ss whether IB supported negative prices, and whilst it's true the drop happened quickly, this was a known likelihood for a few weeks. The fact that IB kept letting people go long at positive prices, knowing they couldn't execute stop loss trades at negative prices is frankly terrible.