I think at the heart of this issue is that employees that tend to say such things feel like in some way they were ignored. "Doing something" does not necessarily mean getting rid of the employee that made the mistake or caused the problem. You don't need to explicitly say, "Yes, we had a talk and discussed ABC and he or she is going to do XYZ", as that is really none of the complainant's business. I think its important to get the full story, including precise details, relay the information back to the complainant and say that you will follow up with it. I think communicating in such a respectful manner to both the complainant and the person being complained about, will have a good impact. I make an effort in my job to try to make it so no one feels like they are ignored, while at the same time not compromising confidentiality.