Who cares? If you were short a stock that was literally worth ZERO, who the hell cares if they covered or not? Is there a bunch of people out there that want a ticker in their portfolio showing a value of ZERO?
Here's what happens. Stock is halted (bankruptcy or fraud, whatever), stock holders are the last to get paid. Shorters are last to get paid as well. The broker would eventually mark the shares to zero and shorters can then cover for a 100% gain. Simple as that.
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