Even if a zero-balance credit card is not used, the account age and available credit limit help a person's credit score.
If the person decides they no longer wish to use the card (e.g. due to a rewards program change that makes it no longer the best option for any category), there is some value in leaving the account open.
Suppose a couple years pass and the account has remained inactive; the card issuer notes that they will close the account for inactivity. The customer agrees, knowing they will not want to use the card in the future, and that if something changes that they do, they might wish to be again eligible for introductory bonuses. For the purpose of this question, please assume the consumer has decided to close the account or allow it to be closed for inactivity.
If the customer has another card from the same issuer, sometimes it is possible to call and close one account by consolidating the credit limit into another one; this option is clearly better for the credit score than closure without consolidation because it retains the higher prior total available credit. For the purpose of this question, suppose that is not an option, either because the customer does not have another card from the same issuer or the issuer has a policy against this.
Which of the two bolded options above is worse for the customer's credit score? For this question, suppose there are no fees associated with either option.
Some sources say that having the bank close the account is worse, because the notation of bank-closed does not distinguish as to the reason why. Other sources say that the reason why is distinguished, and it's better to have an account automatically closed for inactivity than to do a consumer closure just prior to when that would happen.
What's the truth? Is there any reliable source (e.g. information from credit ratings agencies) which can provide evidence one way or another, for credit ratings agencies in a particular jurisdiction?