Here's text from an electronic companion certificate in my bank:

Offer valid for Coach class travel only. Upgrade to Business class or First class (excluding sleeping car accommodations) is available upon full payment of applicable accommodation charges.

This seems ambiguous regarding Acela, since the only way to upgrade to the referenced First Class day seat would be to use the certificate for the baseline fare on Acela, which is Business. There is no published Coach Class.

So....is the certificate good for Acela Business? Perhaps AGR Insider can weigh in.