You stop exposing your store in a public argument
You used to argue over who was right in a public reply, giving more visibility to the disagreement than to the fix. With the habit of acknowledging the problem and moving the case to a private channel, the public reply now shows that the store takes care of people who complain, for anyone who reads the review later.
You give the customer who complained a real answer
You used to leave a case only in the public reply, with no follow-through, so the customer stayed unsure whether anything actually changed. With the habit of keeping the customer posted in private while the case gets resolved, they follow the progress and get an actual fix.
You stop assuming it's fixed and start confirming it
You used to treat sending a new product, a discount, or a refund as closing the case, without checking whether it actually solved things for the customer. With direct confirmation after the fix, you know whether the problem is really over or still needs an adjustment, instead of assuming everything is fine.
You build a record of fixes instead of one-off cases
You used to treat every negative review as its own isolated problem, with no trace of what caused it or what got changed. With the case and the fix logged, even briefly, the store builds a record that helps spot patterns, like a recurring delay, a defective product, or the wrong measurement, before they turn into several similar reviews.
You earn more trust from people who read the review
You used to give the impression, with a defensive public reply, that you don't take criticism well. With a reply that acknowledges the problem without arguing over facts and shows care for the person who complained, anyone who sees the review later sees a store that resolves things, not one that defends itself.