Third party releases are provisions that release non-debtors, such as officers, directors, shareholders, or non-debtor affiliates, from claims and causes of action held by creditors or other non-debtor parties.
As a small shareholder of common stock, I don't think there's any danger of being included in any actions resulting from the bankruptcy proceeding regardless of whether you opt out or not.
I got my notice in the mail last week and simply tossed it in the garbage and will be taking my loss on Form D next year. That'll be the end of the story for me.