A complaint is two things at once
There is a problem to fix and a person who is unhappy. Automation handles the first well and the second badly, because what an upset customer wants is evidence that someone with authority has taken it seriously.
What it should do
Detect the complaint immediately, gather the history, identify what went wrong, draft the response, and route it to a person with everything assembled. That is meaningful work that shortens response time without removing the human.
Automating a complaint response tells an angry customer exactly how much attention they warranted.
Escalate on tone, not just topic
Frustration, repetition, and threats to leave are signals to route to a person regardless of subject. That is escalation on stakes rather than on confidence, applied to emotional stakes.
Never let it decide the remedy
Refunds, credits, and exceptions are judgment calls with financial and precedent consequences, and they belong in the list of things an AI employee may never do alone.
Speed still matters enormously
An immediate acknowledgement that a real person is looking at it defuses more than a perfect answer four hours later. That acknowledgement is safe to automate, and it is most of the benefit.
Mine the pattern afterwards
Complaints clustered by cause are the highest-signal product feedback you have. Reading them as a set is the same practice as reviewing the questions your AI couldn’t answer — and it is what stops the same complaint recurring.