(Kagi dev here)

Being a paid service means Kagi's incentives are different. Instead of selling your data or profiting from feeding into ad-tech food chain, we are interested in selling you a subscription.

We do not associate queries with an account, as a matter of fact we do not save queries at all. You are right that this can not be verified, the question you need to ask yourself is what kind of incentive we have for misusing user data in any way.

Unless users want us to do start using their search history to improve quality of searches (something we may introduce as an option in the future as we've been asked to), we have no reason to do so.