You're focusing on the wrong thing.
Output is not interchangeable with the prompt. In many cases, the prompt does not have the information the sender wanted to give you, and there is no guarantee that your LLM will give those information - or do it correctly - if you use the prompt yourself.
The entire value of here is that sender read the output and is vouching for it. This is where "bits of information" come from. If the sender cannot be trusted to verify and vouch for the LLM text they're sending to you, well, they're an asshole and you should rebuke them or find someone more considerate of others to talk with. Them giving you their prompt doesn't help you with anything.