Delisting does occur, but according to the exchange's policy. Usually after trading below $1.00 for 30 consecutive days. Then they like 6 months to get it back above... it is a process.
How so many former GM shareholders got screwed- thought they would come out, but that stock was halted at one point and made to be like old Nazi Govt Bonds, worthless one day, after few days wait, re-listed GM with same ticker, but new issue stock only had value- Nothing of old shares. Watch for something like happening here I fear...
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