This same thing has happened to me. In general, is it advisable to contact people who are searching for information about your deceased relatives? Is privacy protected when using the PM system to do so? And, what are most people doing with the information (in this case, the poster's words implied that she or he is not a relative)?
Welcome to rootschat PattiD.
Yes, it is safe/private if you contact people via the Personal Messaging System. The admin staff will be able to read your message I think, but not the general public. So if you want to exchange information about anyone who is still living it is advisable to do so privately.
If you have deceased relatives in common then it can be a good idea to post on the appropriate thread as you often find distant cousins this way - people locate rootschat threads often via a google search of ancestor's names, and join up to contribute and make contact. Many of us have found distant and not so distant cousins this way.
It often happens that people do research for others, which is perhaps why you get the impression that the person you refer to may not be a relative. What do they do with the information? Building family trees - either for themselves or others.