The US legal system isn't really set up any particular way with regard to first party admissions. It's just a statement that can be introduced into evidence like any other. Indeed, usually when they are treated specially it's to make them non-admissible. E.g. in an accident, your offer to pay the injured party's medical bills can't be introduced as evidence of fault.
The reason lawyers tell people to clam up is because jurors put great weight on what people say about their own actions. It's precisely the other edge of the sword of what you're talking about--a positive public statement can have a great effect on customers, but one that comes out wrong can have a very bad effect on jurors when the plaintiff brings it up in court.
The reason lawyers tell people to clam up is because jurors put great weight on what people say about their own actions. It's precisely the other edge of the sword of what you're talking about--a positive public statement can have a great effect on customers, but one that comes out wrong can have a very bad effect on jurors when the plaintiff brings it up in court.