A map of complaints also maps who knows how to complain.

Complaint data measures two things at once, what went wrong and who felt able to say so. People with time, confidence, language, and the belief that complaining works are heavily overrepresented, while those with the worst experiences are often the least able to file anything. The map of problems is also a map of access.

If you use feedback to decide where to act, ask which groups are missing from it entirely. Then go and ask them directly rather than waiting. The silence from a particular quarter is data, and it usually points somewhere that needs attention more than the loudest channel does.