Would you consider using the RR from a prior report as a rent comp in a later report to be a violation of confidentiality? If both reports were for the same lender, and they cared to look, it would be clear that you used data you previously agreed to keep confidential. Where would you draw the ethical line?
WRT client requirements, I have called four different lenders to discuss their SoW requirements in their bid offerings. Three times, the lender had no good working understanding of what was actually in their SoW. The exception was calling BoA and they could answer my non-confidentiality questions. So, I don't have strong confidence that I can look to the lender for an interpretation of GBL or the MA data security law.
Suppose that a lender could offer an opinion on how to interpret those laws WRT re-use of data obtained in the course of an assignment. Experience tells me that I can find another lender with a different interpretation which would not agree with the first. So, looking to the lender doesn't work.
The Appraisal Institute would be the next source of authority. Lately, we submitted a question for an interpretation. The manuals all said one thing on the question and the AI contact said a different thing at first and then declined to provide any further guidance. Like the lenders, the AI is not helpful for an interpretation, IMO.
The E&O carrier would be another place to ask for guidance. But, nobody wants to be on the hook for a legal opinion.
So, getting a legal opinion would be the next option. Cost is prohibitive and lawyers can arrive at very different conclusions, just as appraisers can. I worked in a law firm for two years doing property tax and found this to be the case regularly.
Another place you could check would be the state licensing board for discipline actions. Maybe appraisers are being disciplined for mis-use of confidential information? I checked MA, RI, ME, NH, and VT recently on another question. Top reason for discipline was failure to comply with CE requirements. I found no instance of discipline for mis-use of confidential information.
That leaves client instructions to keep information confidential and your office's policy. That is why I posted earlier that appraisers need to know that policy. Our office policy on data security fairly meets the requirements of GBL and the MA data law. Generally, these requirements appear to be more concerned with the physical security or re-sale of the data than the re-use of it, IMO. We don't re-sell data. And a strong argument can be made that any data received from a client that is non-confidential becomes company property for the use of the company in its business. Anticipating objections, an argument made for the opposing position would be sophistry.
Unless the client has explicitly stated that the data is to be confidential, then we use it. Experience has shown that the data usually already lives on CoStar, local MLS, Compstak, or some other platform. Our approach meets my personal test of fairness as integral to ethics.