I was wondering for a long time if it's possible to modify the current scheme where the bought Dark Matter is always spent first to the pattern where DM obtained through expeditions and other gift-awarding events is always debited first from the account instead?

The reason for rearrangement of the scheme is that some players, including myself, are accustomed to utilizing the bought DM as a guaranteed mean of protection against account deletion in case of extended inactivity and associated Vacation Mode for longer than 36 days.

At the moment, this limitation prevents some users from spending the found DM once in a while on small things such as the call of a Merchant or acquisition of certain boosters because any such operation naturally reduces the source of purchased DM to 0 and only then begins withdrawing the freely-obtained part of it, which basically means its collected part gets locked until the customer decides to proceed with another purchase, which isn't usually made only because of that, and is simply postponed.

So in essence, the suggestion's plot is about increasing amenity of how a single premium resource is used for handling both paid and free-of-charge tasks without having each other severely locked out.