I'm not sure what manufacturer you're talking to, but that's not really true, and I'd be a bit suspect of a manufacturer that tells you that. There is a grain of truth in it, but they mark the polarity for a reason.
On of many manufacturer's statement on the topic. Remember, when you get them, they have already been charged in the testing process, so read on.
Eaton supercapacitors are designed with symmetrical electrodes, meaning they are similar in composition. When a supercapacitor is
first assembled, either electrode can be designated positive or negative. Once the supercapacitor is charged for the first time during the 100% QA testing operation, the electrodes become polarized. Every supercapacitor either has a negative stripe or sign denoting polarity.
Another manufacturer with a similar story.
For manufacturing and consistency purposes the terminals are marked with polarity. It is recommended practice to maintain the polarity although catastrophic failure will not occur if the ultracapacitor is reversed charged for some reason. If the ultracapacitor has been conditioned for charge in a certain direction and then is changed, the life can be reduced due to this conditioning. For the PC5, PC10 and PC55 products the case is comprised of stainless steel. Due to the corrosion potential it is required to maintain the polarity indicated on the products, and reverse polarity will cause accelerated life reduction.
