Organic often is ultra pasteurized which makes cream harder to whip, and, IMO, changes the taste for the worse.
Carrageenan, as you say, is a type of seaweed, but I seem to remember reading somewhere that it is altered significantly before being used as a thickener in processed foods. Cream doesn't need it, and I would not buy cream with it for that reason alone. Why encourage companies to mess with our food by telling them (with our money) that we will buy it even if we disapprove?